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MINING

This page primarily focuses on metallurgical mining, though many of the terms, processes, and concepts are the same within the non-metallurgical extraction industry.  These other industry sectors include gas and oil production, non-metallic mining, and aggregate production.  Mining: Water, Power, Rocks, Environment, Society and Labor.

California Mining and Lore

Nevada Mining and Lore

 

 I.        DISCOVERY

 

1.0  Mining Law of 1872 May 10, 1872 (17 Stat. 91, 30 U.S.C. 22 -54).

1.1  Discovery of Mineral Deposit,
1.2  Locating and Recording Mining Claims
1.3  Site Development
1.4  Annual Maintenance

1.5  Mineral Patents.

1.6  Other Mining Laws and Regulations

 

An individual may exercise their fundamental and unalienable right to mine minerals on federally owned land by staking a claim to and on the land.  Upon establishing claim, the individual must maintain the claim to exercise and keep rights for beneficial use of the land and property assets.  The fee-simple title remains with the government. 

 

Before the Federal land Policy and Management Act of 1976 (FLMPA) the claimant had the right to extract minerals and use the surface unimpaired and unqualified. However, the land management agencies, as backed by courts, currently only allow the claimant use of surface as necessary to develop the claim according to provisions of surface management regulations (36 CFR 228, 3209, et. al) promulgated by the land management agency.  This claim remains a taxable private property that can be leased or sold.  When abandonment of the claim, or otherwise defaulted (eminent domain, unpaid taxes, and similar) the property rights revert to federal control. 

 

1.1       What is a Valuable Mineral Deposit

The term Valuable Mineral Deposit is contained, though not described or defined, in the federal statutes.  As such, the government has since developed two definitions.  The first is the economic definition which proscribes to the concept of an economic ore body.  Further development of the concept in case law established the "prudent man rule" in 1894, Castle v.Womble, 19 LD 455 (1894), which provided"...where minerals have been found and the evidence is of such a character that a person of ordinary prudence would be justified in the further expenditure of his labor and means, with a reasonable prospect of success in developing a valuable mine, the requirements of the statutes have been met."

The Supreme Court approved a parallel concept, the marketability test, in U.S. v. Coleman, 290 US 602-603 (1968) which requires that the claimant show a reasonable prospect of selling minerals from a claim – where a profit is a reasonable likelihood.

 

1.2       Locating and Recording Claims

The following site does a great job detailing the process of striking a claim

http://www.theprospector.com/html/howtostakeclaims.html

 

Mining claims

 

Mineral Leasing Act of 1920 removed coal, oil, oil shale and gas, among other minerals (30 USC §§81-287) and the Act of July 23, 1955 (30 USC §612(b)) removed sand, stone, and gravel from the Mining Law of 1872.  Further, in 1913 in Hughes v. Florida, the court determined that as a building material, shell rock is not a locatable mineral under the Mining Law of 1872.   

  •               Locating a load claim

  •                   Locating a placer claim

  •                   Locating a mill site

  •                  Tunnel right

  •                  Amending/patenting mining claims

 

1.3       Site Development

 

1.3.1  Construction of Access and Haul Roads, Rail Spurs and Ports

 

1.3.2  Construction of Mining Buildings and Utilities

Some miners need to build homes, recreation, and stores for their workers, especially when located way out in the boonies of Nevada or Australia.

 

1.3.3  Construction of Beneficiation Facilities

Construction of trams, pipelines, conveyances, leach pads, and processing mills and ponds.


1.4    Annual Maintenance

 

Major recent deliberations regarding the requirements for annual surface work per (30 U.S.C. 28) were decided via UNITED STATES v. LOCKE, [471 U.S. 84 (1985)] and are contained here: http://caselaw.lp.findlaw.com/cgi-bin/getcase.pl?court=us&vol=471&invol=84

 

 

1.5       Mineral Patents.

 

Patented Lands

Through the patent process, a claimant may buy out the fee-simple interest from the government entirely.  The owner of this patented property may abandon rights to the land. For patented rights, the land does not revert to the government but remains private land.  These private lands become ‘inholdings’ surrounded by Federal Land Management Agency (FLMA) land.  New owners of such lands have rights to both access and use of the land, though the FLMA typically impedes such rights.

 

Unpatented Lands Reversion to Federal Control

Unpatented and abandoned mine/mill sites entirely on federal lands may revert to federal control per the establishing and implementing regulations of the federal land management agency having ‘jurisdiction, custody or control of the site. 

 

1.6       Law and Regulations

 

Definition of mining and extraction: The physical and mechanical methods such as blasting and crushing of rock than enables miners to concentrate metal-bearing ores.

 

The following laws and regulations govern not only the mineral extraction and mining activities but all the other ancillary support activities that must also be conducted such as social and environmental work, permitting, and bonding.

 

The godfather of all resource activities is the Mining Act of 1872.  This United States federal law authorizes and governs prospecting and mining for hard rock minerals such as gold and silver on publicly owned lands.  Various provisos apply [http://library.findlaw.com/1999/Jan/1/241491.html] though extraction can generally proceed without any compensation provided to taxpayers should activities meet and stay within certain thresholds and parameters.  No royalties are collected by the Federal Government.  It codifies the system of acquiring mining claims on public land that was formed in California and Nevada in the late 1840s, 1850s, and 1860s, during the California gold rush.

 

Primary Laws and Regulations Governing Mining

 

Abandoned mine reclamation funds 30 CFR Part 872.  The Office of Surface Mining provides some information here:

http://www.osmre.gov/federalregister/44fr67057.txt

 

Mining has always been one of the more regulated industries in the US.  Parts of the following laws and regulations govern mining today:

 

  • Clean Air Act (42 U.S.C. 7401 et seq.)

  • Clean Water Act (33 U.S.C. 1251 et seq.),

  • Federal Land Policy and Management Act of 1976 (90 Stat. 2743,
    43 U.S.C. 1701 et seq.),
    part of which redefines claim recording procedures and provides for abandonment if the procedures are not followed.

  • Forestry Act of 1897

  • The Mineral Leasing Act of 1920 (which made certain nonmetallic minerals not open to claim staking)

  • The Mineral Materials Act of 1947, which provides for the sale or public giveaway of certain minerals, such as sand or gravel.

  • The Multiple Mineral Use Act of 1954, which provided for the development of multiple minerals on the same tracts of public land;

  • The Multiple Surface Use Mining Act of 1955, which withdrew common varieties from mineral entry; and

  • Mining and Mineral Policy Act of 1970.

            (Promulgated per Department Of Interior [DOI] Mining and Minerals Policy, 1973) 

  • Mining Law of 1872 May 10, 1872 (17 Stat. 91, 30 U.S.C. 22 -54).

  • USC Title 12 Chapter 2 Subchapter 1V

  • National Environmental Policy Act of 1969 (42 U.S.C. 4332(2)(C))

  • Public land authority in 43 U.S.C,.2, 1201 and 1457

  • Resource Conservation and Recovery Act (42 U.S.C. 6901 et seq.), as required under 43 CFR part 3800.

  • Rural Abandoned Mine Program 7 CFR

  • Southern Nevada Public Lands Management Act

  • Surface Resources Act of 1955 (69 Stat. 367, 30 U.S.C. 601-615),

  • Surface Mining Control and Reclamation Act of 1975

  • Gold Confiscation Act of May 21, 1933 (U.S. Treasury Act 416F)

  • Unlawful Occupancy and Inclosures of Public Lands Act (43 U.S.C. 1061 et seq.)

  • Comprehensive Environmental Response, Compensation and Liability Act [aka 'Superfund']

  • Emergency Planning and Community Right to Know Act

  • Solid Waste Disposal Act

  • Safe Drinking Water Act

  • Migratory Bird Treaty Act

  • Toxic Substances Control Act

  • Endangered Species Act

  • National Historic Preservation Act

  • Native American Graves Protection and Repatriation Act

  • Federal Mine Safety and Health Act of 1977 (Mine Act)

 

 

Interior Department Regulations

Title 43; Chapter II - Department of Interior

http://www.access.gpo.gov/nara/cfr/waisidx_00/43cfrv2_00.html

Bureau of Land Managements (BLM's) 1980 Regulations 43 CFR part 3800,

 

Restrictions on Patented Land Use

http://www.nplnews.com/library/1872mininglaw/occupancy/jul161996-43cfr3715.htm

 

CALIFORNIA CODE OF REGULATIONS

TITLE 14. Natural Resources

Division 2. Department of Conservation

Chapter 8. Mining and Geology

Subchapter 1. State Mining and Geology Board

Article 1. Surface Mining and Reclamation Practice

 

NEVADA REVISED STATUES AND NEVADA ADMINISTRATIVE CODE

 

II. EXPLORATION

 

Exploration entails the prospecting, sampling, mapping, drilling and other exploratory work involved in searching for properties containing commercially viable ore.

 

Let’s go over each step in detail.

 

Goals:

Define valuable information on mineralogy, structure, alteration patterns and the controls on precious metal mineralization

 

NOTE: A ‘qualified person’ under the governing regulations (e.g.  Canada’s National Instrument 43-101) such as a qualified and certified geologist typically oversees exploration and development field work including drilling activities.

 

2.1 Prospecting/Surveying

2.2 Sampling

2.3 Mapping

2.4 Drilling

2.5 Ore Assay

2.6 Pre-Feasibility Study

 

2.1       Prospecting/Surveying

 

Prospectors find gold.  They may use many forms and techniques to discover gold deposits and ore bodies, some quite advanced and many as old as the hills themselves.]

 

There is no one right way (the right method is the one that yields economical metal recovery); some discoveries are incidental or even accidental.  Prospecting does, however, require tools, technique, time and money and a fair amount of good luck (education may sometimes partially suffice).  During the 1800's prospectors used tools such as a pickaxe and shovel and picked their targets using their knowledge of geology, read of the lay of the land, and relying on a fair amount of luck.  Modern prospecting forms the basis of an exploration program  which utilizes several tools to target potential sources of commercial grade commodity ores - the target of the initial exploration.

 

Desk-top surveying includes review of geologic geophysical and aerial maps and previous mining locations and production values.

 

Field sampling may include review of previously published data and remote sensing.  Remote sensing can be accomplished through both satellite or field aerial reconnaissance.   Each ore body is comprised of minerals that have unique physical properties such as grain size and crystalline structure.  These physical properties, in turn, determine how a mineral will absorb and reflect sunlight.  Remote sensing survey's will pick up on the a properties unique absorption and reflection of light - a spectral signature.  This technique works better in certain geographic basin than others.  For instance: http://www.digistar.mb.ca/minsci/finding/remote1.htm
 

Geologists also use remote sensing as a remedial cleanup tool.  Many modern environmental remediation methods were born of the mining industry.  The same techniques first use to find the minerals in a ore are also used to find minerals released into the environment.  Here is a write-up on use of remote sensing in remediation techniques:

 

http://www.emporia.edu/earthsci/student/lawrence1/lawrence.htm

 

Surveying also includes geophysical methods such as seismic refraction which can determining the composition of material underground by inducting a shock wave and then, using sensitive geophones, recording the time it takes for that wave to bounce off a buried body of rock and return to the surface.  This technique will identify geologic formations that may provide favorable mineral targets.

 

2.2       Sampling

 

Mining is a matter of milligrams and tons.  The metal or other sought material must be present in both amounts and form that warrants setting up an operation and investing further resources.  Grades are determined by the amount of metal per volume and can be expressed as a percentage such as ounces per ton or milligrams per kilograms.  The amounts are expressed as volumes such as cubic yards or as mass, such as tons.  See Weights and Measures for additional information on measurements.

 

Simple surface determinations

 

Bulk-till sampling is a sampling protocol or process used to determine the mineralization grade of glacial till. Typically, samples are developed either via backhoe trenching or a standard reverse circulation drill rig to develop a series of soil samples from the area of glacially deposited till. The samples are then assayed under a microscope to determine particle counts.

 

Samples must meet standards for Precision, Accuracy, Representativeness, Comparability and Completeness (PARCC). These standards provide that the data set represents actual conditions of the media that was sampled (Precision); Provides a very close approximation of actual conditions in the media (Accuracy); Provides a true view of the overall media resource, and not just some sub-set thereof (Representativeness), can be replicated and analyzed next to other similar data sets collected for the same reasons from the same media (Comparability); and gives a full picture indication of the likely conditions that will be encountered throughout the data set and media (Completeness).

 

These requirements are simple in theory but extremely difficult to provide in a field sampling program.  Often numerous phases of data collection are necessary to provide that these indicators are fully met.

 

Metallurgical and Geotechnical Testing and Determinations

 

Soil science provides the basic sampling and determination methodology that miners employ first to determine if the first few feet of earth show promise that warrants exploration into deeper earth.  The Russians developed modern soil science, the Germans developed modern geologic methods, and the Americans developed modern hard rock mining determinations and technology.  (All very generally, mining goes back thousands of years, of course)

 

Initial Soil and Metallurgical Determinations

Plasticity, Percolation texts, compaction and density tests are typically conducted surface sampling methods that can be accomplished with minor expenditures because the samples can be collected almost directly from the surface. All soil sampling is actually on the mineral portion of the soil. The organic material, i.e. ‘duff’ (in soil science parlance the Oi, Oa,and Oe horizons) is scraped off the surface and the underlying mineral soil (in soil science parlance, the ‘A’ horizon) is collected and analyzed.

 

Drilling test work may follow surface tests, should surface sampling prove promising.

 

2.3    Mapping

 

Geological mapping support the intent to provide sufficient information necessary to prepare a resource estimate of gold resources.

 

2.4       Drilling

 

A proper drilling program determines the extents of the mineralization down dip and along strike.  Different drilling goals may require differing drilling techniques and methodologies.

 

Resource definition drilling:

Pre-feasibility

Feasibility study

 

Phase I Drilling

Exploration geologists use drill rigs to collect samples from cores of ore bodies beneath the surface with the intents to gather a representative samples that may determine whether further exploration is warranted.

 

Drill Program Design

 

Long-hole open stope: A method of mining involving the drilling of holes up to 90 feet long into an orebody and then blasting a slice of rock that falls into an open space. The broken rock is extracted and the resulting open chamber is not filled with supporting material.

 

Exploratory Shafts: The installation of a collar made of concrete and timber around the mouth of a shaft/drill hole

 

2.4.1  Drilling Types

 

Air Rotary:  This drilling method uses air pumped from a tank at the surface, down through the drilling rods and back up the circular ring to the surface; simultaneously cooling the drill bits while also keeping the borehole from collapsing inward.  The re-circulated air brings drill cuttings back to the surface.

 

Cone Penetrometer: Actually a direct push, rather than a drilling technology, cone penetrometers (CPTs) push rather than drill through a soil via large force exerted by a truck on the surface.  The inserted cone is able measure soil properties.

 

Diamond:  Drilling with a hollow bit and a diamond cutting rim produces a cylindrical core that is used for geotechnical and geological study and assays. Used in minerals exploration.

 

Direct Push: A surface mounted truck, using static weight and vertical force, pushes a sampling core barrel directly into the soil, collecting samples, measurements, and readings. 

 

Geoprobe: A direct push, rather than a drilling technology, the geoprobe can be advanced through soil using either a percussion hammer or direct force.  These rigs can be mounted on relatively small trucks, useful for initial soil sampling – especially in tight areas.

 

Large Diameter Boreholes: Using an auger drill with bucket, the tool ends rotates in soil, stops and raises. The cuttings are them dumped into the waste pile.

 

Mud Rotary: This drilling method uses a water/bentonite (clay) slurry that is pumped from a tank at the surface, down through the drilling rods, and back up the circular ring to the surface, where the slurry (mud) is recycled. This methodology both cools the drill bits while also keeping the borehole from collapsing inward.  Additionally, the circulated mud brings the drill cuttings back to the surface where they settle and then are removed (or disposed with the mud) from the slurry tank.

 

Percussion Drilling:  The simplest yet very effective drilling method using an engine or percussion-powered and cable-driven core and barrel sampler can be placed in almost any situation yet produce fine cuttings of 80-90% (minus 8 mesh).  These folks did a great write-up on their model:

 

http://www.consallen.com/forager/cable-tool/cable-tool-drilling.htm

 

Reverse Circulation (RC): Used in hard host rock and for deeper depth, this drilling technique produces rock chips rather than core.  The chips are forced by air to the surface and are collected for examination and analysis.  This technique is both faster and cheaper than diamond drilling.

 

Rotary air blast (RAB) Drilling: An air percussion reciprocating piston drives a hardened, hollow steel core with hardened tungsten or carbide bits into hard host rock.  Recirculated air pushed sampling material up along the outside of the steel rod, along the host rock.  Since RAB can drill hardened host rock, the mining industry typically used this drilling method for initial large scale sampling programs with necessary drill depths between 10 and 150 meters.

 

Rotosonic Drilling: A dual barrel sampler within an outer casing, encrusted with hardened carbide bits, penetrate soil through use of vibration and rotational force.

 

2.4.2  Drilling Methods

 

Condemnation Drilling

A systematic condemnation drilling program

 

Goal: To show there is no economically significant metal mineralization on a property. This type of drilling design typically serves one of three purposes: A) The land owner is trying to determine that cutoff grades are insufficient to continue exploration (finding the edge of the economical lode). B) The landowner is trying to utilize or transfer the lands for other purposes. C) Legal dispute over land and the holding party wants to show that the land is not as valuable as another party may claim.

 

Infill Drilling  Diamond drilling at shorter intervals between existing holes, used to provide greater geological detail and to help establish reserve estimates.

 

Developers must focus on Infill drilling, the placement of new drilling bores within areas of previously quantified resources or known previous production. Canon in the resource extraction industry provides that the best place to find gold is where you find it and the next best place is where somebody else had previously found it.

 

As such, new drilling programs on previously unidentified, quantified, or known production areas provides additional risk.  This additional risk provided hopeful developers with the nickname ‘wildcatters’, those looking for resources in areas not previously determined by drilling, sampling, assay and geochemical results. 

 

Of course, as with any venture, the riskier the venture the more profitable the potential return. Those that can find a new economically developable resource put themselves in a fine point for selling out their claim, or first rights on production.

 

The new potential development basin, simply because it is new and unproven, may have a hard time attracting standard potential then those production basin with proven and known production history and potential.  The greater risk, though, provides willing investors with a greater potential return on their capital.

 

Drilling Program Objectives
Determine and outline indicated and inferred mineral resources
Establish economic feasibility of production based upon a gross metal value per tonne cut-off.

Sometimes results are presented as Gross Equivalent Ounce. (GEO). In this case other metals are considered as a credit of gold.  For example, the ore may have 10 ounces of gold and enough copper and silver to equal the monetary value of two ounces of gold - hence the ore is rich in 12 Gross equivalent ounces.

 

The drill hole plan and drilling field work requires oversight of a Qualified Person.

 

Drill Results

Drillers report results within an initial drill program, pre-feasibility study or feasibility studyHere is on example of how drill results are presented, as shown by Pelangio Mines, Inc., reported in June, 2006:

 

Table: Drill Hole Data
---------------------------------------------------------------------------------------------
HOLE         COLLAR       AZIMUTH      DIP                FINAL
NUMBER   LOCATION   (DEGREES)  (DEGREES)  DEPTH(METRES)
----------------------------------------------------------------------------------------------
PM-113       18560E         180               50                  270
                     20135N
---------------------------------------------------------------------------------------------
PM-114       18480E         180               50                  303
                    20135N

 --------------------------------------------------------------------------------------------

 

The following table presents results from a pre-feasibility study conducted by Golden Star at two African properties. The full results can be found at:

 

http://www.gsr.com/Operations/WestAfrican.asp

 

Note in this example showing results from the pre-feasibility study, has more information than the results provided in the table above.  The further along an exploration program goes, the higher order of information is provided.

 

 

North

East

From

(m)

To

(m)

Dip

Azimuth

Intersection

(m)

True Width

(m)

Grade

(g/t)

Benso

 

 

 

 

 

 

 

 

 

BERB302

57485

175512

12.0

21.0

-50

90

9.0

6.9

3.42

BERB058

58034

176720

1.0

21.0

-50

90

20.0

15.3

1.75

BERB145

58501

176962

22.0

30.0

-50

90

8.0

6.1

22.04

Hwini-Butre

 

 

 

 

 

 

 

 

HBRB0001

32759

176934

0.0

6.0

-50

90

6.0

4.6

4.54

HBRB0002

32759

176958

9.0

12.0

-50

90

3.0

2.3

19.65

HBRB0021

32811

176805

0.0

9.0

-50

90

9.0

6.9

19.52

HBRB0034

33015

176543

17.0

29.0

-50

90

12.0

9.2

3.64

HBRB0044

33119

176298

2.0

10.0

-50

90

8.0

6.1

3.42

HBRB0094

33369

176318

0.0

18.0

-50

90

18.0

13.8

2.89

HBRB0095

33419

176318

0.0

22.0

-50

90

22.0

16.9

3.46

HBRB0097

33442

176334

0.0

11.0

-50

90

11.0

8.4

9.84

HBRB0175

34496

176200

9.0

15.0

-50

90

6.0

4.6

5.58

HBRB0253

32659

177145

1.0

7.0

-50

90

6.0

4.6

3.24

HBRB0325

33208

177191

11.0

20.0

-50

90

9.0

6.9

 

 

 

Are these grades good?

 

The following are considered 'high grades' for the purposes of most North and South drilling programs: Greater than 5 g/t gold and 15 g/t silver

 

(NOTE: this was the company's version of what a high grade means, and they specifically referred to their particular deposit. CoinMIne prefers results above 10.0 g/t gold and 20 g/t silver when a by-product of gold mining; and levels over 40g/t per specific silver deposits.)

 

The grades really come down to how rich the strike is, multiplied by size of the ore body.  The economic viability depends on whether or not the deposit can be developed via surface mining, or if underground workings are required.  For example, 7.5 grams per ton/gold (gpt) is a fine sample when representative of an ore body that requires underground mining, as long as the vein is at least 1 meter wide and many meters long.  A miner will need to determine if multiple underground veins are present, with similar grades.  If only one vein lies underground, the capital effort  required to access the vein is likely not worth it.  On the other hand, 7.5 gpt proves quite a rich target for open pit mining.  Miners construct most open pit mines on ore bodies way under an average of 7.5 gpt.

 

What is the difference between cut and uncut grades?

 

A 'cut' result actually refers to grade, or value.  For statistical analysis, assays may only be reported above a somewhat arbitrary minimum and below an arbitrary maximum.  The value is only somewhat arbitrary because the cut grade typically considers previously known grade averages of a property.  The cut value only reports those figures above the arbitrary minimum and/or below the maximum to eliminate 'outliers' - those very high or very low samples that are not reflective of the actual ore body.  Throwing out these outliers for statistical averaging purposes provides a better picture of overall property grades.

 

Hence 'uncut' results are true assay values.

 

Phase II Drilling

A miner may conduct second phase drilling to confirm gold mineralization controls or provide a comparison with grades in nearby holes.

 

Percussion drilling producing fine cuttings (80-90% -80 mesh) with a split sample is used to assay for target metals.

 

North American Drillers

            Drift Exploration Drilling from High River, Alberta

 

2.5       Ore Assay

 

Ore is an economic resource known as a reserve. Ores grades are reported as a percentage by weight.

 

For explanation purposes, when a sample is reported as a percentage (%) of 1.0% or 5.0% per short ton (2000 lbs ) [Note a 'tonne' is approximately 2204 lbs.  See Weights and Measures for more information];

 

Then:

  • 1.0% produces 20 lbs metal per ton

  • 5.0% produces 100 lbs per ton.

                    

North American Assay Companies

  • American Assay and Environmental Laboratory Reno, Nv

  • Skyline in Tuscon, Az.

  • Cone in Denver

  • Bondar Clegg in British Columbia

  • Chemex in Sparks, Nv (Was Bondar Clegg prior to Dec. 1, 2001).

  • Inspectorate American Corporation, Sparks

  • ALS Chemex; Guadalejara, Mexico

  • Acme Analytical Laboratories in Vancouver.

  • G&T Laboratories in Kamloops, British Columbia, Canada

  • Swastika Laboratories Ltd. in Swastika, Ontario.

 

International Assay Companies
Ammtec Laboratories in Australia.
TransWorld Laboratories in Tarkwa, Ghana
SRK Cardiff
BSI in Lima, Peru
Inspectorate Services Laboratory,
Peru

 

2.5.1  Sample Preparation

 

Laboratories prepare samples for analysis by drying and heating the samples for a couple days so that the moisture leaves the ore and the assay can be reported as dry results.  The samples are dried in large walk-in ovens kept around 170 degrees Fahrenheit.

All soil properties, with the exception of color, hue and chroma should be defined for dry soil samples.

 

Once drying is complete, sieving and jaw-crushing is employed to get the sample size such that 90% will pass through a #10 mesh sieve (2.00mm diameter).

 

Next, the laboratory will prepare a standard1,000-gram subsample by pulverizing with large capacity ring and pulverizing bar or puck pulverizer so that 90% passes through a #150 mesh.  When I worked at Bondar-Clegg in Sparks, Nv during the late 1980’s we used mechanical pulverizers that were essentially a series of heavy metal rings that sat on a vibration bar.  The vibrations would crush the ore sample between the metal rings, producing an ever finer competent sample.

 

Once the fine subsample is prepared, laboratories have a variety of analyses and assay options at their command. 

 

 

2.5.2  Assay Methodology

 

Some of the most commonly used assay analyses in the mineral production industry include Fire Assay, Bulk Leach Extractable Gold sample (BLEG)/Leachwell analysis (an accelerated cyanide sample leach), Inductively Coupled Plasma, atomic emission spectrometry, and atomic absorption.

 

Many samples assayed for gold, especially, are done by fire assay fusion and finished with either gravimetric or Atomic Absorption analysis.  Since property owners need to also know the levels of base metals in their ore to conduct mining plans, they request the laboratories provide analyses of these base metals too. 

 

Typically, copper, lead, zinc, silver and two dozen additional elements are assayed by acid digestion and then finished with Atomic Absorption or Inductively Coupled Plasma (ICP) 32 element suite analysis.

 

Gold Assay Methods

 

ALS Chemex has developed a very nice page describing and showing the various analytical methods currently used to determine gold (or other metal) percentage in ore:

 

http://www.alschemex.com/learnmore/learnmore-techinfo-preciousmetals-gold.htm#Advantages%20of%20the%20Fire%20Assay%20Process

 

Accuracy methods and standards [US standards used herein] provide utmost concern, since all further exploration and economic decisions will be based upon reported laboratory analyses.

 

When exploratory samples are reported as ppb, typically geochemical methodology was the methodology used for Au determination.  Assays are reported as parts per million (ppm).  Economically minable results are typically reported via assay. 

 

Wet geochemical analysis is important to determine other metals and elements present in minor or trace amounts.  This is important to know during the mine planning stage, especially when designing the processing circuit, because presence of various elements may favor selection of one process over another, or indicate a need for various types of pre-treatment. 

 

Metal determinations by gravimetric finish require that competing metals in the same column of the periodic chart are completely separate before conducting analysis.  For example, if you are looking for gold content in an ore sample and have not completely removed the silver from the ore than the result produced by gravimetric finish will provide false low results for silver and overly high results for gold since the reading of metals is now biased toward gold (the metal being sought in the analysis).  Since gravimeters measure acceleration of an object, that object affected by gravity, the gravimetric method determines weight in samples by differentiating weight in an ore.  Typically, gravimetric finish also implies the use of spectrometry.

 

 2.5.3  Quality Assurance and Quality Control

In addition to the myriad standard analysis methods available to today’s assayers and laboratories, there are – of course- a host of other not-quite-so-legitimate assay techniques that have been peddled by scammers (ala Bre-X in the 1990s). 

 

Additionally there have been plenty of times where sheer errors in application and execution of technique have caused numerous problems (ala Lassen Mining in the 1980’s), the miner missed the orebody potential (to be later picked up by the next individual who either applied a better technique or waited a few decades for the better technique to be invented. 

 

For example, much of Nevada’s current gold production supply was either unassayable, undetectable, or unavailable to mining techniques of last century’s miners. However, today’s cyanide technology has made mass amounts of economical gold available to the Carlin Trend and elsewhere. 

 

One underhanded technique is development of a drill core, then grinding the entire core sample into a powder which would then be assayed.  Typically, the core is split and only 25% or 50% is set to the laboratory for further analysis. The remainder is saved and can either be assayed again in the future as a split or duplicate sample, or archived for future analysis or posterity.

 

I know of geologists that, when examining a property for potential development, have looked back at cores develop two or three decades ago. These core samples provide a visual history of the past investigation and development program on a property.  Some mines have core samples laying around at several hundred foot levels that were left there when the mine last operated many decades ago.

 

Regrettably, when the entire sample is pulverized, the temptation and opportunity (a dangerous combination) exists for altering (tampering) or ‘salting’ (adding precious metal flour to) the sample. 

 

As such, the industry has developed quality assurance and control protocols to ensure the integrity of their geologic program.  The analytical laboratory community has developed their own Quality Assurance-Quality Control (QA/QC) programs to ensure the integrity of their analysis and reporting.  And geologists follow standard statistical analysis methodology to provide clarity and transparency in their results. So too, the regulatory interests added their own standard reporting methods.

 

To prevent these errors or fraud, all sampling programs, analytical analyses, and reporting are subject to QA/QC programs.  The QA/QC program provides systematic and rigorous methods for data Validation and Control to ensure the sample data is not corrupted with false positives or negatives.

 

Examples of QA/QC Programs – Drilling and Sampling

 

Drill programs require a QA/QC program to assist in estimating reserves. The QA/QC program may entail regular insertion and analysis of blanks and standards to monitor laboratory performance. Blanks are used to check for contamination.  Duplicate samples are two samples collected from the same core but submitted separately.  Standards check for grade-dependence variance and biases and are also used to calibrate sampling equipment.

 

The exploration geologist will typically provide duplicate samples to another laboratory for analysis of the same metals. 

 

Sometimes the geologist will have a third assay conducted by different analytical methods.  Often samples with a certain cutoff grade, such as 10g Au/t, might be treated with pulp and metallic sieve analysis and then compared to analyses and results provided via other analytical methods such as fire assay.

 

The size, type and texture of the sample provides a challenge.  Laboratories need to minimize the innate heterogeneity of a large sample (over 1kg) that coarse samples provide in order to arrive at the most accurate assay possible.  Course samples are often re-assayed via metallic screen fire method – generally considered a better analysis for coarse gold samples although the assay is known to report gold percentages of up to 5% higher than standard fire assays.

 

An example (QAQC) sampling program may provide that known samples with certified gold content (standards) are inserted every 20 or 25 samples (depending upon the total sample size submitted for analysis).  Similarly, blanks could be inserted every 20 samples with field duplicates every 25 samples.

 

Depending upon the goals of the investigation program, analysis standards, blanks and duplicates could comprise as little at 10% or as great as 20% off the total sample assays. 

 

Examples of QA/QC Programs – Analytical and Assays

 

Course samples, from which the sub samples were prepared, provide part of the QA/QC program because portions of the course sample undergo the same analysis and the fine samples.  Reject blanks (known barren parent material), duplicates, splits, and standard blanks can all be run through the same analytical process as the fine samples to serve as blinds.  Duplicates provided to another laboratory serve as double-blind samples.

 

For instance, a geologist could design a drilling program where 5% of samples are blanks or duplicates.  The analytical laboratory will employ their own QA/QC program regarding method blanks, and certified standards to determine accuracy, consistency, and precision their analyses when compared to previously prepared and analyzed ‘standards prepared for the analytical method.  Furthermore, the geologists could request the laboratory employ even more rigorous or additional QA/QC checks to ensure sample and data integrity.

 

Examples of QA/QC Programs – Results Reporting

 

Ores grades are reported as a percentage as parts mineral per weight. Reporting could be done, for example, as grams per ton (g/t), parts per million (ppm) or parts per billion (ppb).

 

Laboratories may use third party independent contractors to conduct data validation. These data validators use statistical and mathematical models to ensure data integrity.

 

 

2.6       Pre-Feasibility Study

 

Goals:

  • Estimated a capital cost to develop economic resources on property (hopefully within approximately 20% level of accuracy regarding costs);

  • Identify million tonnes per annum operation productivity target;

  • Determine average ounces per annum and total year mine life (and build in assumptions regarding average operating cost per ounce production);

  • Estimate a Net Present Value ("NPV") using a constant gold price per ounce at a set discount rate (such as 5%), based on indicated resources that were developed via the drilling program;

  • Determine indicated resources in million ounces and grade in grams per ton.

  • Determine probable reserves in grams per ton and total ounces.

 

 

Confirm and Demonstrate Land Ownership and Rights

 

Patenting

 

In the US, if a company has a patent, they own it. When patented, the applicant is issued a title.  However, a 'staked' claim is unpatented and therefore conveys no ownership rights to the property.  Also, see section 1.5.

 

Patent=title=ownership

 

Properties

Do properties meet NI 43-101 standards.

Mineral Rights

Water Rights

Credits

 

Determining Reserves

 

In determining reserves, the competent person designs an economically

optimized pit based on all operating and mining costs.  Reserves are modeled to a cut-off grade, reserve material that is demonstrated to be technically and economically feasible to extract.

 

Scoping Study

 

The scoping study may entail three components:

 

  • Independent Reserve Study

  • Develop power and water source;

  • Design and implement drill program

 

Goals:  Gather information sufficient to move project into Preliminary Feasibility Study phase.

 

Objectives:

  • Determine and outline indicated and inferred mineral resources

  • Establish economic feasibility of production based upon a gross metal value per tonne cut-off

 

(Requires Qualified Person)

 

Reporting Standards

Mining companies use Technical Reports to report reserves and resources, technical definitions for ore assets.

 

In determining reserves, the competent person designs an economically

optimized pit based on all operating and mining costs. Reserves are modeled to a cut-off grade, reserve material that is demonstrated to be technically and economically feasible to extract.

 

The standards that govern these reports and their underpinning methodology are contained in various regulations, industry guidance, and regulatory body decision rules.  These reporting regulations include: The Private Securities Litigation Reform Act of 1995

 

Reserves calculation according to National Instrument 43-101 -- Standards of Disclosure for Mineral Projects (NI 43-101 standards), differ significantly from the calculations and reserve disclosure guidance promulgated under U.S. Securities and Exchange Commission Industry Guide 7.  Industry Guide 7’ requires a "final" or "bankable" feasibility study in order to disclose and publish calculated reserves. Note that Proven and Probable’ reserves disclosed under NI 43-101 are not considered reserves under U.S. Securities and Exchange Commission Industry Guide 7.

 

Note:  This will effect mining company valuation!

 

The 12 Dirty Little Words of Mining Exploration

 

Any financial report or marketing statement that uses the following list of qualifiers must ensure that the terms meet previously published standards; these terms have exact, legally defined, meanings and must be used as such in publications:

 

"seek", "anticipate", "believe", "plan", "estimate", "expect" and "intend" and statements that an event or result "may", "will", "should", "could" or "might"

 

Oxide vs. refractory ore

 

One extremely important part of the pre-feasibility study is making ht determination on how to process ore to retrieve economic metals.  The type of host rock and ore that will be unearthed drives this analysis.

 

Oxide ore has already undergone weathering and chemical processes of oxidation which make the ore amenable to leaching recovery.  Refractory ore is less amenable to leachate due to silica or sulfide encapsulation or higher carbons presence.  Any ore that does not respond to conventional mineral processing (cyanidation) to produce acceptable product recoveries without an intermediate step to address its refractory attributes (usually some form of oxidation).

 

For example, the CoinMine has long been interested in Bema Gold’s properties, including Cerro Casale. 

 

Cerro Casale has returned some very impressive amounts via exploration programs but becomes challenging when the pre-feasibility looks at treatment methodologies because both Cu and Au are available in large quantities buy low grades. The primary metallurgical problem regards oxides, especially Cu oxides (and carbonates) present in ore.   Since this mineral specie is cyanide reactive (when cyanide as CNO is introduced into solution leach the Au,  the Cu also goes into solution hence the dore product has unacceptable Cu levels (mostly aesthesis are unappealing - ‘red-bar’).

 

Any problems with recovery will drive up operating costs and impact mining valuation.

 

Reporting Reserves

 

Mining reserve estimates must be conducted by a primary qualified person. 

 

Reserves are typically reported as oxide and refractory ore.  Often a company will report the total percentage of each type of ore.  Reserves are typically reported with an assumed percent of dilution allowance for waste rock and another efficiency percentage typically in the high 90th percentile.  Refractory ores require bio-oxidation treatment, a processing method where bacteria oxidizes refractory sulfide ore such that it is then amenable to normal oxide ore processing techniques such as gravity separation followed by carbon-in-leach (CIL).

 

Additionally, the mining company will usually indicate what percentage of the reserves they have an interest in.  Many times companies form partnerships or joint ventures, pooling resources to develop a property they could not otherwise bank on their own.  In these cases they have percentage claims of the ore body, which may change after various ownership transfers or other financing agreements.

 

 

Mineral Resource Summary

 

Open Pit

Underground

 

Reserves are:

            Indicated Resource

            Inferred Resource

 

Underground

 

            Indicated Resource

            Inferred Resource

 

+

 

Open Pit Reserves

            Deposit Indicated Resource

 

=

 

Total Inferred (non reserve) material

 

  • Pit optimization studies

  • Pit Optimization Results (Drilling results in grade and tones)

 

 

Pre-Feasibility Study vs Preliminary Assessment vs Bankable Feasibility Study

 

Very generally, the pre-feasibility study summarizes the exploration phase and recommends whether or not the ore grades justify moving the project into the next phase, the preliminary assessment.  The preliminary assessment introduces and analyses economic, regulatory and social inputs with the goal of providing enough information and analysis to recommend the next phase, the bankable feasibility study (BFS). The BFS goal is to thoroughly examining al project inputs to determine if the sites ore can be economically mined given all other financial, regulatory, social, and environmental conditions.

 

 

 

III.      PRELIMINARY ASSESSMENT

 

3.1.      Exploration and engineering activities

 

  • Previous Metallurgical Work and Current Recommendations

  • Block model

  • Pit Optimization

 

3.2       Mineral Resource Estimate

 

GOAL: Upgrade inferred resources to indicated or measured resources.

 

Drill hole spatial density varies, being more concentrated on known resources and less concentrated on the lode periphery.  FQ, NQ, PQ holes (tool/index sleeve diameter) are drilled from surface. BQTK holes are drilled from below ground.

 

Resources estimate methodology

 

Geotechnical drill core testing >

Test results help determine pit design parameters.

Interpret drill intercepts in cross section,

  • Coding samples,

  • Capping assays,

  • Compositing to vein thicknesses, and

  • Estimating grades and thicknesses of each vein separately

  • Develop three dimensional grade thickness models

 

Resource may be estimated by ordinary kriging of 5 x 5 x 5 foot blocks.  These results are then translated (called ‘reblocking’) to larger 10 x 10 x 20 foot blocks. This size reflects the practical constraints anticipated with typical proposed open pit mining methods.

 

Calculation and reporting of reserves must follow the regulations and guidance used in the country of origination is which the corporation was established.  For instance, Canadian forms calculate and report according to NI 43-101 whereas US firms report to standards of Exchange Commission Industry Guide 7.

 

3.3       Economic Analysis

 

GOAL:  Estimate potential financial results that development will provide using assumptions of mining method (open pit/underground etc.) and milling operations.

 

Economic analysis requires estimation of both costs and production. Cost estimates are generalized at the Pre-feasibility stage to reflect industry standards and averages. A typical estimate may be shown as:

  • Overburden mining costs - US$1.25 per tonne of material;

  • Rock mining costs - US$1.50 per tonne of material;

  • Processing costs - US$12.00 per tonne ore;

  • General Administration costs - US$5.00 per tonne ore;

  • Plant Gold recovery - 95%; and

  • Assume 50% of existing underground workings backfilled with material having a density of 2.0.

Actual production costs widely vary and depend upon many site specific factors.

 

3.4       Pit Optimization Studies

 

- Target gold price

- Strip ratio of about 11:1

(based on measured and indicated mineralized materials with known and inferred ounces per tonne.)

- Mineral resources are the basis of this economic assessment.

 

3.5       Economic analysis

 

Fundamental economic analyses are driven by the pit optimization study; those facts derived from the optimization study and the underlying assumptions built by the study that feed the economic model.  The goal with the economic analysis is to build the cost model that will provide an estimate of the net present value (NPV) of mineral resources.  This economic model will be used twofold. First, the model will determine the feasibility of conducting further analysis and work at the ore body and second the model will underpin future fundraising and other financing efforts.

 

3.5.1   Pit Economics

 

3.5.2   Production Inputs and Statistics

 

Open Pit Ore

  • (Tonnes, Recovery, Total Gold)

  • Waste Rock (Tonnes)

  • Waste Till (Tonnes)

 

Production Ounces Ore

  • Open Pit

  • Underground

  • Total

 

Metal Sales

  • Gold

  • Silver

  • Base Metals

 

Royalties

 

Operating Costs

  • Mining

  • Processing

  • Load to Crusher

  • Ore Processing

  • General and Administrative

 

Cost per Ton Ore

Cost per Ounce Gold

 

Net Profit pre-tax

Capital Investment

Working Capital

 

Equipment Salvage

Pre-production mining

Net capital costs

Net cash flow

Cumulative cash flow

 

GOAL: Provide Goals for Preliminary Assessment and Bankable FS

  • Check sample a minimum of 10% mineralized zone by metallic assay zones using a zero cut-off.

  • Complete mini-bulk sample gravity checks on all drill hole composite samples.

  • Design and complete a bulk sampling program

  • Estimate "flow ore" mineralization types.

  • Determine differences between grade model and actual mineralization.

 

3.6       Key Assumptions and Parameters in an Economic Analysis.

 

Mining Operations and Costs

 

Operating costs (2005)

  • US $3.00 per ton mining cost,

  • $1.50 per ton waste mining,

  • $21.00 per ton milling cost,

  • $3.85 per ton general and administrative cost,

  • $19.50 per ton trucking cost.

 

Milling Operations and Costs

 

Own Milling – Where the company construction and operates its own new mill at the project site. This becomes the ‘(base case’ for economic modeling.  In some cases the operator may import a mill from another location or upgrade a previously existing mill.

 

Toll Milling – Where the company enters into an agreement with an already operable mill to accept, on fee basis, their product for milling and treatment.

 

Cost Assumptions

Estimator’s model projected costs, using boilerplate model programs and standard mine planning software packages, reflect recent actual mining costs from the same or nearby and similar properties, or contract mining quotes.

 

These costs are extremely variable as quotes only reflect a certain period of time and known conditions. Modelers must input variability and contingencies.

 

Estimators must estimate or establish the following”

 

  • A discount rate (for example  5%) to calculate NPV.

 

  • Mine life (example 6.5 years based upon the optimized mine plan and mine schedule

 

  • Production rate (Example, 100,000 tonnes per year).

In Canada the production rate must comply with provisions per the governing Mines Act or Environmental Assessment Act.

 

  • Capital costs (environmental, closure and rehabilitation)

 

  • Realized metal prices (per production, sold forward, and hedged)

Increasingly tricky yet important is estimating the currency exchange rates, especially over a relatively long mine life.

 

Bottom line, the economic analysis must provide managers and investors enough confidence in the predicted economic viability of the project to fund the next steps (additional permits and investigation and development) necessary to turn a property into production.

 

3.7 Develop Annual Mine Plan

 

The mine plan is developed first at the Conceptual Mine Plan during the Preliminary Assessment and then at the Engineered Design Stage during the Feasibility Study.

 

Conceptual Mine Plan

The definition of a mine varies upon use, purpose and jurisdiction.  In the broadest sense, a mine refers to an area of land from which mineral or metal ores is economically extracted including those areas where minerals are beneficiated including supporting infrastructure such as mills, roads, tailing ponds, ventilation shafts, etc.

 

Use open pit modeling software such as Whittle 4D to produce an economic pit shell and outline total of in-pit resources using an estimated concentration of each recoverable ore (ton and percentage) at a minimum ton cutoff (such as $20/ton).

 

You can order the latest version of Whittle here: http://www.gemcomsoftware.com/whittle41kit/

Develop expected mine life.

 

Determine pit design parameters.

 

3.7.1.  Develop process flowsheet

The flowsheet process should provide for the conditioning and sizing (following separation processes) of feed material and the prescribed treatment process that will allow metal recovery

 

Some of the guidelines a mining engineer must consider when developing process flowsheets are:
Processing costs are more expensive than extraction costs
Sulphides are more expensive than oxides.
Oxides can be leached.

Sulphides must be crushed then roasted before milling.

 

3.7.2 Determine Mill Feed Rate

 

The Preliminary Assessment requires development of a mill feed rate (in tonnes per year. As an example, a figure of 5 million tonnes per year could be used to calculate the secondary rates and averages that feed into the economic model.

 

3.7.3   Determine Average Head Grade

 

Typical ranges, for example might range from 1.0 to 1.8 g/t of PM in the first five years of mining, and 0.5 to 1.0 g/t in the last five years.  The decreasing figure accounts for playing out of the lode and a mill that produces constantly diminishing returns.

 

3.7.4   Conduct Metallurgical studies on Core Samples

(See section 2.5.3)

 

3.7.5   Determine Mining Methodology

 

A standard example for conventional mill circuit utilizing an oxide ore feed might utilize crushing, grinding and two-stage flotation.

 

3.7.6   Determine Head Grade Driven Concentrator Recoveries

(i.e. palladium 75%, gold 70%, copper 70% and nickel 75%.)

 

3.7.7   Determine Mining Costs

 

Percentage mined vs. percentage processed

Property Interests

(Who owns what percentage of resources; who pays what percentage of exploration; who pays what percentage of operation)

Financing

Labor

Power

Water

Permitting/Environmental

 

 

3.7.8.  Business Model

 

Every going concern requires a business plan when starting out.  Mining is no exception.  In fact the large capital required to bring a mine on line, through the nefarious and various vagaries required just to commence production – as detailed above, forces the mining business model to meet exacting standards. The initial and secondary financing required to meet the large sums of start up capital rely upon sound business plans; the markets consistently drive home this point as can be seen by large fluctuations in miner company share price when major inputs to the business model, especially government support, environmental permits, and labor change significantly.

 

Customers and Competition

Risk Factors

 

Increasing Mine Plan Productivity

a) Extend reserves along strike and at depth in currently known ore bodies,

b) Provide greater definition of additional deposits amongst inferred resources,

c) Increase infill drilling amongst inferred resources via drill definition of targets previously identified via surface geochemistry computed from more widely spaced drilling, and

d) Increase drilling amongst ore anomalies and high grade shoot extensions

 

3.8    Grade Control

 

Mike McKevitt, Principal Mine Geologist, Golder Associates, teaches a great course on this topic and covers:

 

• Grade control and sampling theory

• Sampling methods and practice in open pit and underground mines

• Sample preparation, assaying and geochemical analysis

• Tools for quality control

• Cut-off grade determination

• Delineation and mark-out of mineable ore blocks

• Statistical and geostatistical foundations of ore block estimation

• Sources and methods for control of dilution and ore loss

• Comparisons between open pit and underground grade control systems

• Practical mining of ore blocks, stockpile control and classification of ore and waste

• Reconciliation between ore reserves, grade control and production

• Ore Block Optimization and other applications using conditional simulation

 

3.9      Smelting and Refining

 

3.10       Administrative

 

3.11    Environmental

 

3.12    Socio-economic Activities

 

Empowerment, Community involvement and service,

Relocation of displaced residents

 

3.13    Example and Sample Preliminary Assessment

 

This sample table was developed by Anooraq for their South African properties and is available at:

www.anooraqresources.com

 

 

--------------------------------------------------------------------
In-Pit Resources (constrained to 32-year pit)
Ore                                        tonnes        160 million
Waste                                      tonnes        274 million
Cut-off Grade                               GMV/t(i)   Approx. 10.50
Strip Ratio                             Waste:ore              1.7:1
--------------------------------------------------------------------
Milling rate                                 t/yr          5 million
--------------------------------------------------------------------
Average Grades (Life of Mine)
Pt                                            g/t               0.44
Pd                                            g/t               0.53
Au                                            g/t               0.08
Ni                                           kg/t               1.21
Cu                                           kg/t               0.83
--------------------------------------------------------------------
Metal Produced in Concentrate (Annually)
Pt                                             oz             53,300
Pd                                             oz             63,400
Au                                             oz              9,900
Ni                                            lbs          9,998,000
Cu                                            lbs          7,250,000
--------------------------------------------------------------------
 
(i) GMV/tonne is the sum of the grade multiplied by metal price,
    using 75% recoveries for Pt, Pd, Au and Ni and 80% recovery for
    Cu.
 
Capital and Operating Costs
 
--------------------------------------------------------------------
Capital Cost Summary
Mining Pre-production            US$ 12.8 million
Plant and Infrastructure        US$ 135.0 million
Socio-Economics                   US$ 5.0 million
--------------------------------------------------------------------
Total                           US$ 152.8 million
--------------------------------------------------------------------
Operating Cost Summary
Mining                                      US$/t               3.84
Environmental/Reclamation                   US$/t               0.14
Processing                                  US$/t               5.36
Administration                              US$/t               0.18
Total (milled)                              US$/t               9.52
--------------------------------------------------------------------
Metal Prices
--------------------------------------------------------------------
Platinum                                   US$/oz                650
Palladium                                  US$/oz                250
Gold                                       US$/oz                375
Nickel                                     US$/lb               4.00
Copper                                     US$/lb               1.00
Foreign Exchange                      ZAR:US$ 7:1
--------------------------------------------------------------------
Results
--------------------------------------------------------------------
Net Revenues                         US$/t milled              14.88
NPV(ii) - 5% discount           US$ 300.5 million
NPV(ii) - 10% discount          US$ 138.8 million
IRR(ii)                                        25%
Project payback                        3 yr, 3 mo.
All-in cash costs per
 Pt-eq oz in concentrate(iii)             US$ 337
Net Cash flow - 32 years        US$ 715.2 million
--------------------------------------------------------------------
 
(ii)  NPV and IRR are calculated on a pre-tax and royalty basis
(iii) Pt-equivalent ounces are calculated by converting all metal
      values to a gross metal value, at the metal prices above, and
      then dividing by the price of platinum.
 

ASSUMPTIONS

 

- An independent Qualified Person (QP), per Standards of Disclosure for Mineral Projects defined by National Instrument 43-101(NI 43-101), developed block model, pit optimization work, in-pit resource estimate, and mineral resource estimates.

 

- These estimates formed the basis for the Preliminary Assessment.

 

- The Preliminary Assessment contains sufficient data and mining scenario whereby the project can proceed to the Bankable Feasibility Study (BFS).

 

 

 

IV.     FEASIBILITY STUDY

 

4.0       DESCRIPTION OF PROPERTY

 

The Bankable Feasibility Study (FS) provides the backbone of analyses that will determiner whether a mining property sees the light of production, or is passed onto the slag heap called “What could have been” (or, in many cases, “What will be, given future increases in metal prices”.)

 

Summary of:

  • Land Ownership

  • Exploration

  • Operations

 

4.1 Parameters and Key Results:

 

The Discussion on Measured and Indicated Mineral Resources

 

Provide sensitivity analysis on key parameters:

  • Expected Capital Costs

  • Expected Operating Costs

  • Expected Cash Flow

  • Reserve Estimation

 

Other risk factors

Price of outputs: Price of metals and exchange rates

Price of inputs,

Energy risks

Interest Rates

·        Construction project risks (general uncertainties in engineering and construction costs)

·        Fraud

 

4.1.1 GRADES

 

Grade: the amount of valuable mineral in each ton of ore, expressed as troy ounces per ton or grams per tonne for precious metals and as a percentage for other metals.

Cut-off grade: the minimum metal grade at which an orebody can be economically mined.

Millhead grade: metal content of mined ore going into a mill for processing. Usually lower than reserve grade because of dilution by non-ore grade materials.

Recovered grade: actual metal content of ore determined after processing.

Reserve grade: estimated metal content of an orebody, based on reserve calculations.

 

RESOURCES and RESERVES

 

Mineral Resources

            Indicated

            Inferred

Mineral Reserves

Proven           

Probable

 

These terms are defined separately and differently in various gold producing countries.  Although reporting standards were fashioned by each county to have similar intents and goals such as relaying confidence levels and disclosures, the approaches and definitions differ between each country.  Nevertheless, the terms are generally standardized between Canada, the US, and Australia.  Terms do vary in South Africa.

 

In Canada, reporting requirements for disclosure of mineral properties are governed by National Instrument 43-101 (“NI 43-101”) and further promulgated in Canadian Securities handbook. The definitions given in NI 43-101 are adopted from those given by the Canadian Institute of Mining Metallurgy and Petroleum.

 

United States (US) reporting requirements for disclosure of mineral properties are provided governed by SEC Industry Guide 7.  The United States Geological Survey promulgates reporting requirements.

 

Both resource and reserve numbers must be released under a Professional Engineer or Geologist independent of the mining concern. Whenever a mining company publicly releases resources or reserves, or drilling results presented in other term, it must be done under the approval of a registered and independent Engineer or Geologist

 

Canadian Terminology under NI 43-101

 

As defined in a Canadian Securities handbook and Code of Federal Regulations (Regulatory Cite) produced in conjunction with the TSE and are covered under CFR43-101. These terms are also standard for use in Oz and the US.

 

Mineral Resource

Mineral Resource - Refers to natural, solid, inorganic or fossilized organic concentrated material in such form and quantity that provides a grade that provides a reasonable prospect for economic extraction.

 

Indicated

Indicated Mineral Resource - Refers to that part of a mineral resource with enough established characteristics of both
quantity and quality such that they can be sufficiently estimated to support mine planning and evaluation based upon economic viability of the deposit.

 

Inferred

Inferred Mineral Resource - Refers to that part of a mineral resource where quantity, grade or quality can be estimated on the basis of geological evidence and limited sampling. Ore quantities and qualities are considered reasonably assumed, but not verified.

 

(NOTE: “Inferred mineral resources." Is a term recognized and required by Canadian regulations. However, the U.S. Securities and Exchange Commission does not recognize the term.)

 

Measured

Measured Mineral Resource - Refers to that part of a mineral resource with enough established characteristics of both quantity and quality such that they can be sufficiently estimated to support evaluation and planning of economic viability and production.

 

RESERVES

 

Mineral Reserve - Refers to the economically mineable part of a measured or indicated mineral resource (ore body) demonstrated by at least a preliminary Feasibility Study (FS). The FS must include adequate information on economic, metallurgical, mining, processing and other relevant factors which demonstrates economic ore extraction at the time of FS reporting. Mineral reserve calculations include diluting materials and loss allowances during mining.

 

Probable

Probable Mineral Reserve - Refers to the economically mineable part of an indicated (and sometimes a measured mineral resource) demonstrated by at least a preliminary feasibility study.

 

Proven

Proven Mineral Reserve - Refers to that economically mineable portion of a measured mineral resource demonstrated by at least a preliminary feasibility study.  The tonnage difference between Probable and Proven is the sum of non-economic ore removed from economic ore.

 

United State Terminology Under SEC Industry Guide 7

[NOTE: As CoinMine is a US concern, US terms and definitions are used throughout this web site and related materials unless specifically stated otherwise.]

 

RESOURCES

Resources are mineralized materials without sufficient quantified or qualified data necessary to be considered reserves.

 

Inferred, Indicated and Measured resources under SEC 7 are substantially similar to the NI 43-101 definitions.

 

RESERVES

 

Reserve - A type of resource that has proven economic potential based upon a feasibility study.  A reserve refers to that part of a mineral deposit which could be economically extracted at the time of reserve determination. Reserves must be supported by a feasibility study done to bankable standards that demonstrates the economic extraction. A “Bankable Feasibility Study" requires standard analysis that implies confidence levels developed in the study provides sufficient eligibility for the project to receive external debt financing.

 

Probable - Refers to reserves with estimation similar to that used for proven reserves, but the data points (inspection locations, sampling, etc.) are either spaced further apart or otherwise less adequately determined.  Nevertheless, the degree of assurance is high enough to assume continuity between observation points.

 

Proven (Measured) - Refers to reserves where:

(a) Quantity is computed from revealed dimensions or drill holes from which; grade and/or quality are computed from the results of detailed sampling; and

(b) Where the sites for inspection, sampling and measurement so closely spaced and where geologic character is so defined that the mineral content of reserves are well-established.

 

The tonnage difference between Probable and Proven is the sum of non-economic ore removed from economic ore.

 

Summary of Terms

 

RESOURCE

RESERVE

Inferred

Not Applicable (EVER!)

Indicated

Probable

Measured

Proven

 

Also see further resources:

·                     U.S. Geological Survey Circular 831, 1980

·                     Principles of a Resource/Reserve Classification for Minerals by the U.S. Bureau of Mines and the U.S. Geological Survey

·                     A revision of the classification system published as U.S. Geological Survey Bulletin 1450-A

 

4.2       FEDERAL MINERALS

Locatable – Locatable minerals depend upon economics and as such cannot be provided in any one complete list.  Most minerals are both locatable and

 

Leasable – US Department of Interior regulations originally defined locatable minerals as having three qualities:

  • Prove the land more valuable by their existence,

  • Are recognized by standards experts as a mineral

  • Are not subject to disposal under another law.

 

Salable  

 

Aggregates (sand, clay etc.) are not salable.

 

Use of salable minerals requires either A) sales contract or B) Free use permit.
 

Sales Contract on BLM lands are regulated by Title 43, Code of Federal Regulations (CFR), Part 3600.

 

Free Use Permits are only issued to Government agencies or a nonprofit organization.

 

Sales Contracts on National Forest System lands, regulated by Title 36 CFR Subpart C, 228.40, typically require a Special Use Permit.

 

4.3       Mine Plan - Engineered Design Stage

 

GOAL: Summarize the following:

  • Environmental Conditions

  • Hydrogeology, hydrology, etc.

  • Provide overview of Mineral Geotechnics and geotechnical investigation

  • Present executive summary of mine design, engineering requirements, and planning

  • Summarize environmental and social impact assessment and mitigation measures

 

4.3.1.  Describe Mechanized Materials Handling and Initial Mine Development Structures

 

Provide description on the combination of decline and vertical shafts and drifts.

 

4.3.2.  Describe Processing and Recovery Processes:

e.g. conventional crushing, semi-autogenous grinding and ball milling, followed by gravity separation and carbon-in-leach treatment before gold refining.

 

4.3.3.  Describe Production Levels

 

Define expected metallurgical recovery n percentage terms (e.g. 96%)

 

4.3.4   Establish cut off grade

 

Host Rock

Physical and chemical properties of the host rock determine production and recovery rates. Physical properties include hardness (measured per Moh's scale), formation and stratification.  Chemical properties include mineralization.  

 

Style of Deposit.  Vein deposition provides the most economical removal because the orebody is compact, easily defined, easily recognized, and easily recovered.  Most of the easily accessed (near the surface) vein deposits have already been mined.  Remaining deposits are more expansive and disseminated.  Large amounts of metals are distributed across very large areas in very low grades.

 

Depth of Deposit.  Deposits near the surface can have much lower concentrations of valuable minerals than those at lower depths. 

 

These factors help estimators and modelers develop bulk volume estimates and cutoff grade estimates.

 

Assumptions for Example Cutoff Grade: 1.0 ounce per ton (opt)

  • Continuity along strike and down dip is sufficient so that a mine plan can be developed.

  • Geochemistry can be more complicated with higher cutoff grades.

  • Dilution is limited to 1 meter width.

  • Narrow vein mining techniques

 

Assumptions for Example Cutoff Grade: 0.20 to 0 .25 opt

  • Needs sufficient orebody size for bulk mining methodologies.

  • Simple geochemistry

  • An older mine that already has most capital costs paid.

 

 

4.3.5   Establish Mine Life

 

Define Pre-production period

Determine Full production rates in terms of ounces

Establish expected amount of metal description over life of mine

Establish labor levels and pre-production and full production levels

 

4.4.      Establish Capital Costs

 

4.4.1   Cost of Mine

4.4.2   Cost of Mill

4.4.3   Cost of tailing, Rock and Materials Storage

4.4.4   Cost of Water

4.4.5   Cost of Power

 

4.5       Establish Operating Costs

 

This component provides some of the most difficult problems in the mining industry.  Determining what something will cost in the future provided make-or-break inputs for many industries; in mining, only more so.  Many other industries and sectors have enjoyed relatively stable product pricing power, the amount their product will bear on the open market, due to either stable demand, stable external costs, and especially subsidies and tariffs.

 

Mining does not enjoy such luxuries.  There had been periods in America’s past where either the price of precious metals on the open market was set by the government (or the government prevented open market trading).  At other times the US Government actually set subsidies for the production of precious metals, especially silver in the last quarter of the 19th century.

 

Too, during periods of war the government has also set tariffs for certain metals needed in production of war material. For example, the price of Barium had been set up until the subsidy was removed in 1947.  Removal of this subsidy meant that one of the largest barium mines in the lower 48 states (El Portal, Ca) could no longer produce wares and turn a profit.  During WWII the government also set prices and markets for other industrial metals and, more importantly, massively shifted market demand by substituting metals in the composition of currency (silver, nickel, zinc).

 

Capital costs required for startup and production through pre-production phase

 

Annual operating cost in terms of Dollars per tonne

 

Determine cash cost of each ounce gold produced in terms of dollar per ounce

 

4.5.1 Cost of Mining

4.5.2 Cost of Milling

4.5.3 Administrative Costs

4.5.4 Community Support

4.5.5 Other Social Costs

           

 

4.6.      Determine Cash Costs

 

Cash Cost: The cost of production at the mine site, not including head office costs, interest expense, capitalized development, or stripping, off-site costs (like smelting or refining costs), taxes, or depreciation.

Total Cash Costs (aka 'Mine Site Costs'): Cash Costs plus off-site costs, head office costs, and sometimes interest.
Total Costs: Total Cash Costs plus depreciation, interest, and reported taxes (not necessarily paid).
All-in Cash Costs: Cash Costs plus exploration expense, head office costs, and sustaining capital.'

 

4.7.      Determine Cash Flow

Expected average cash flow value per year

Expected cash flow over life of mine

 

4.8       Establish re-tax Net Present Value

 

(build in discount rate in terms of dollars (e.g.US$150 million) (ZAR 900.3 million)

Determine Internal Rate of Return (e.g. 18.9%)

 

4.9       State Feasibility Results

 

Supporting Studies

Technical Report on the Feasibility Study

Environmental & permitting, tailings, water supply

Infrastructure Study

Administrative, Compensation and Benefits Study

 

 

V.      DESIGN

 

5.0       Mine Plant and Process Design

 

5.1 Mine Design

 

Mining design must first consider the scale of the operation.  Small scale mining may simply consist of a one or two person operation conducted on an erratic schedule.  Large scale mining consists of a regular process involving specialized labor and equipment.

 

The proper mining process depends on the ore mineralogy. Generally, the process design includes:

 

A) Conduct metallurgical testing

B) Develop an ore recovery flowsheet

C) Determine most efficient recovery process based upon local inputs

D) Determine commercial viability of the following major mining processes:

  1. Infrastructure development

  2. Extraction/Production

  3. Pre-treatment

      a. Separation

      b. Flotation

      c. Refractory ore processing

  1. Treatment/Recovery

  2. Beneficiation and Processing

  3. Milling

  4. Reclamation

 

Large scale mining includes both above ground and below ground operations.

 

5.2       Above Ground

 

A) Metallurgical Testing

B) Recovery Flowsheet

C) Recovery Process

D) Commercial Viability Analysis

1. Infrastructure Development

2. Extraction and Production

3. Pre-Treatment

            a. Separation

 Separation via Gravity

 

Separation works because gold is heavier than almost every other element found in ore and is heavier than the ore itself.  Gold has a specific gravity of 19.3 whereas ore, the rock surrounding the elemental gold which you wish to separate from the metal, has a specific gravity ranging between 2 and 3. The main goal is to orient the gold within the column of material and then physically separate out the gold through a series of repetitive motions that rely on gravity to settle out the gold. 

 

The separation process will only succeed if the average particle size is relatively homogenous so that physical agitation can render out the heavier particles.  Should the gold still be bound within large chunks of earth, the separation process cannot succeed. The miners pan in the river works because nature has already separated out the flakes of gold into the stream bottom, consisting of fines such as gravel and sand.

 

The miner then simply finishes the physical separation process by swirling around the slurry so that gravity pulls out the heavier gold flakes into the bottom of the pan. Likewise, dry separation on placer lands works because colluvial action, the geologic process whereby gravity pulls down rocks from mountains, and alluvial action, the movement of material within a water column, has already separated the gold throughout a fairly homogenous lense of earth.  The miner simply finishes the job through repetitive mechanical motions.

 

Other methods for gravity separation:

  • Pans

  • Sluice boxes

  • Rocker boxes

  • Jigs: Pleitz Jig used for separation of nuggets from soil.

  • Spirals

  • Shaking tables

  • Centrifugal concentrators

  • Dry washers

 

Separation via Flotation

 

Flotation processes used in mining were developed base upon wastewater treatment technology. The premise is the same in each case: concentration and settlement of matter. In mining the mineral concentrate is formed through addition of chemical conditioning agents then followed by settlement via mechanical agitation.

 

As with wastewater treatment goals to produce ‘floc’, chemicals are added to mineral slurry in order to produce ‘float’, a foam mixture of targeted minerals. 

 

Alternately, the chemical conditioning can be engineered to weight the flotation of other minerals and aid the physical separation. Typically, multiple chemical treatment steps are required with generally involved bulk flotation products targeted for a flotation process designed to increase metal concentration.

 

Flotation process produces gold with a rather coarse particle size. This reduces grinding costs.  Mechanical agitation may include forced air circulation, known as air sparging, of agitated ore slurry which then develops a foam rich in mineral concentrate. At that point the foam can be separated via skimming.  One key to keep flotation costs economical is the wise use of chemical additives that can either be re-used or disposed of as a non-hazardous waste.

 

Since we know that gold doesn’t float, how is gold separated?  Flotation often occurs where metal recovery also produces base metal by-products.  Flotation separation process becomes most suitable when the gold is in association with (form of ore) sulfides.

For example, where gold is found in association with pyrite, the gold is surrounded by pyrite in an iron sulfide crystal which will form float. The idea is very similar to how soap works. The soap forms structure around the dirt. Although the dirt particle is heavy, the surrounding soap bubble is light and therefore easily washed away.  In mining, the flotation concentrates are then shipped to the smelting facility for metal recovery.

 

b. Flotation

 

Flotation is typically a pre-treatment for Cyanide leach recovery. The ore mineralogy determines the most economical process.

 

c. Refractory Ore Processing

 

Refractory ore processing

Refractory ore processing is conducted simply to pre-treat ore that will not produce metal vial typical cyanide leaching processes.  Almost always, the refractory ore treatment process is followed by conventional cyanide leaching. 

 

Refractory ore processing methods include:

 

1. Bioleaching/Bioleaching: The use of bacteria in solution to strip sulfur.

 

      2. Autoclaving (pressure oxidation) High pressure autoclaves that can operate under either acidic or alkaline conditions use a reactor uses chemical reaction and the physical processes of heat and pressure to oxidize sulfur.  This changes sulphide ore into oxide ores that can than be processed via standard techniques.

 

3. Roasting

Roasting separates sulfur from ore through heat. Since roasting emits sulfur dioxide to the environment and therefore requires scrubbers to change sulfur dioxide into sulfuric acid. 

Non sulfide Refractory ores include antimony, arsenic, pyrrhotite (iron sulfide), and tellurides. Carbonaceous and gold copper ores with high copper contents also prove difficult to process.

 

4. Chlorination

5. Pre-oxidation using Nitric Acid

6. Lime/caustic pretreatment

 

4. Extraction/Treatment/Recovery

 

Pre-Treatment

 

Processing and Milling

Series of grinding mills produce the aggregate into a slurry powder

 

Treatment/Recovery

 

5. Beneficiation and Processing

 

Economically recoverable base and precious metals must be separated from the waste material, also known as gangue - the ore containing minerals below economic recovery value.  There are several ways  of accomplishing this, collectively knows as beneficiation or processing.

 

Amalgamation

 

Although still used by artesian mines in third world countries and small operations elsewhere, the amalgamation days are largely over in industrialized areas due to the high toxicity of mercury and subsequent abolishment via legislation.

 

Cyanidation

 

Cyanide salts are used in silver and gold mining, called the cyanide process. The high-grade ore is finely ground and mixed with the cyanide solution (concentration of about two kilograms NaCN per tonne).  Low-grade ores are stacked into heaps and sprayed with cyanide solution, again with concentration - expressed as [ ] of about one kg NaCN per tonne.

 

Cyanide is highly reactive; it decomposes rapidly in sunlight. It can mobilize some heavy metals like mercury (if mercury is present).  The cyanide leaching process began in the late 1800s and quickly replaced other common gold treatments of the day, such as mercury amalgamation.  Mercury amalgamation, with gold recovery rates commonly between 55-60% is not as efficient as cyanide treatment with recovery rates around 90%. Additionally, as mercury effects on human health became more widely known the process fell into disfavor.

 

As mining technology continually improves, older ore bodies and even tailing piles can again yield economical recovery loads. Examples include the Standard Mine in Nevada most recently utilized by Apollo Gold and the Robinson Mine/Pit currently operated by Quadra Mining (QUA.To).

 

Cyanide leachate process depends upon starting with ore that has been separated, pretreated and ground so that the average particle size will fit through a number-200 mesh screen.

 

A slurry is developed by adding sodium cyanide to ore combined with water. Quick lime is added to keep this slurry mixture with a basic pH, around 11.  The amount of lime and sodium cyanide required depends upon the type of ore being processed. Required cyanide amounts can vary between 1-4 pounds per short ton of ore.

 

The miner must not only maintain the chemical properties of the slurry, but also the physical properties such as percentage of solids. This is important because the slurry must move through a series of agitator mixing tanks.  If the composition is not set right, the settlement will not properly occur. Settlement time also depends upon the capacity size of the agitator system. 

 

Retention or residence time is how long the slurry must remain in the agitator, typically between 12-36 hours.  The great enemy of retention/residence time formulas in short circuiting, where passage of material through a reactor finds a short cut and does not follow the entire engineering/process route.  For this too, the miner-operator must exert continuous vigilance.

 

Once the metal has separated from the slurry the liquid component is then decanted.  This process may require further chemical treatment in a thickening tank.  Also, vacuum filters in series followed by tailings washing can remove both the remaining metal and cyanide precipitated from the solution. At this point the slurry is known as pregnant solution.  The gold recover process used at this stage is usually zinc precipitation and cyanide is removed via the procedure known as counter current decantation (CCD). The solution can then be reused for additional leaching.

 

The precious-metal cations bind to the cyanide anions and forms soluble cyanide. The pregnant liquor is separated from the leftover dirt, which is discarded to a tailing pond or spent (the recoverable gold having been removed ) heap.  The metal is recovered from the pregnant solution with zinc dust that replaces the gold in solution or by absorption onto activated carbon.

 

Although cyanide has become the industry standard, other leaching agents, known as lixiviants, can be used for specific types of ore. For example sulfuric acid may be used in copper and uranium recovery.  In-situ cyanide leachate treatment is the modern, though controversial, method for uranium recovery.

 

 

Other lixiviants

1.      Bromides (Acid and Alkaline)

2.      Chlorides

3.      Sulfuric acid

4.      Thiosulfate

5.      Thiourrea

 

Cyanidation is the processes currently in favor amongst worldwide mining operations due to the economic application.

 

The Cyanidation process will typically include some or all of the following operations:

 

3.1          Agitated tank leaching

3.2          Heap leaching

3.3            Carbon adsorption recovery

  • Carbon-In-Pulp (CIP)

  • Carbon-In-Leach (CIL)

  • Carbon-In-Column (CIC)

3.4          Zinc precipitation recovery

 

3.1       Agitated tank leaching

 

Agitated cyanide leaching in a tank is the fastest method for processing gold. This process can remove up to 90% of gold in high quality source ore once the ore has been made very fine through stamping and milling.  Agitated tank leaching has the advantage of not requiring large amounts of space and can be conducted indoor which also allow continuous processing even during inclement temperature and climate.  Additionally, agitated leaching is a very quick process compared to other types of processing methods. 

 

Some of the drawbacks of agitated leaching are:

·        Very energy intensive

·        Requires solid/liquid separation before processing

·        Requires intensive disposal or reclamation of tailing spoils

·        Requires ore with high gold content and a small particle size (200 mesh)

 

3.2       Heap leaching

 

Design heap leach pad and environmental effects and permits required.

 

Heap leaching allows the profitable recovery of gold in ores that were previously considered played out.  This process requires the ore is laid out in a confined and lined basin where cyanide is evenly distributed over the ore.  Gold, in the pregnant cyanide solution, is then recoverable at the bottom of the pile.  Gold is extracted from the solution via carbon adsorption or zinc precipitation and the barren solution is then reused in the system. 

 

Heap leaching has gained favor, especially in Australia and Nevada, because it provides economical recovery on ores with very low gold contents, down to 0.01 oz/ton. 

 

Some of the drawbacks of heap leaching are:

Ineffectiveness in cold weather

Problems with precipitation input

Problems with adequately and evenly precipitating solution over all ore, especially in ores with high clay contents

Environmental effects

 

These drawbacks, especially the environmental issues have caused great concern amongst many communities in geographic areas with potential economic ores but without a strong mining economy.  For instance, Argentina in general is currently anti-cyanide.

 

The mine plan should summarize the environmental and social impact assessment and required permits for the tailings dam.

 

3.4       Zinc precipitation recovery

 

Zinc Shaving/Precipitation

Zinc shavings in barrels served as an early mining process. The process was simple and worked on both gold and silver via simple substitution.  However, the process was not very effective and did not enable the amount of recovery necessary especially for lesser ore bodies.

 

Merrill Crowe

 

The Merrill Crowe process replaced zinc precipitation after WWI.

A pregnant/clarified solution is passed through de-aeration towers so that oxygen can be removed from solution.  At this point zinc powder is added and the resultant gold precipitation is recovered on a plate and frame filter press

 

One rule of thumb is that ore with a silver:gold ratio of 4:1 or more could still use Merrill Crowe process.

 

3.4       Carbon Adsorption Recovery

 

Stripping

(Gold removed from carbon via caustic solution)

 

Granular activated carbon effectively recovers gold from cyanide solutions in a variety of applications such as fluidized bed columns or slurry leach/separation.

Activated carbon adsorbs gold cyanide old which is then treated with hot caustic and cyanide to reverse adsorption – effectively stripping carbon of gold. The gold can then be removed from solution by electro winning.

 

Carbon-In-Pulp (CIP)

 

Carbon-in-pulp recovery does not require liquid separation for leached ores and instead uses gravity separation or filters.  The leached and solubized ore has activated carbon added to the leach slurry where is adsorbs gold from out of the slurry solution.  Screening and processing in agitation tanks removes the gold from the carbon.  Since gold is finer than carbon, these smaller particles will pass through a smaller mesh size than the carbon.

 

Carbon-In-Leach (CIL)

 

Carbon-in-leach integrates both the leaching and carbon-in-pulp process. Leach tanks are retrofitted with carbon retention screens – removing CIP tanks from the process.  Instead, carbon is added to leach. The carbon adsorbs gold as soon as the gold separated from the cyanide.

 

CIL proves especially useful processing gold ore with naturally high carbon percentages as the activated carbon will preferentially remove gold, preventing the native carbon from "preg-robbing" (removing gold from the pregnant solution) the valuable ore and holding onto the gold rather than allowing separation.

 

The carbon added in CIL is more active than native carbon, so the gold will be preferentially adsorbed by carbon that can be recovered for stripping. The CIL process will frequently be used in small cyanide mills to reduce the complexity and cost of the circuit.

 

Carbon-In-Column (CIC)

 

Carbon-In-Column (CIC) employs pregnant solution flowing through fluidized bed columns set up in series.  The flow is up - against gravity – in these columns allowing recovery of metal ore from heap leach solution. 

 

These columns separate our solids from ‘thick’ solution, removing the solids.  The heap is then flowed reverse through columns, with gravity, allowing gold, but not carbon, to settle out through the filters in column.

 

Countercurrent Decantation (CCD)

 

 

6. Milling

 

A series of grinding mills produce aggregate into a slurry powder.

 

 

Surface Mine Design

1. Optimization Algorithm for Mining Pit Design

2. Floating Cone

3. Lerchs-Grossman

4. Critical Factors

 

4.1Strip Ratio

 

Pre-stripping and inventory build-up.

 

Before the crushing section, grinding circuit, and the CIL plant are hot commissioned (operated with material), many tones of ore must be crushed and staged at the crushed ore stockpile.

 

4.2  Ore Tonnes

4.3  Ounces Produced

5.0  Net Present Value (as is NPV Curve)

 

The best situation is where heterogeneous grades allow establishing a 'starter pit'.  This is where a higher grade zone will allow establishment of a pit that has low production costs but high return.  This provides immediate capital expenditure return establishes operations at the mine.

 

7. Reclamation

 

 

6.0 Below Ground

 

A) Metallurgical Testing

B) Recovery Flowsheet

C) Recovery Process

D) Commercial Viability Analysis

1. Infrastructure Development

2. Extraction and Production

3. Pre-Treatment

a. Separation

Gravity separation

 

b. Flotation

c. Refractory Ore Processing

4. Treatment/Recovery

5. Beneficiation

6. Processing and Milling

7. Reclamation

 

Underground

 

The two primary underground mining production methods are variation of stoping techniques called Room and Pillar and Shrinkage Stoping.  Proper stope design is critical in any mine plan.  Since the stope is where the ore is first broken. Stopes also provide ventilation and access ways into ore removal areas. 

 

Room and Pillar

The miners remove ore in such a manner that rectangular rooms are excavated from bedrock.  The rooms have support columns, called pillars, which bear the load of the rock above to prevent collapse. The miners can build multiple layers of rooms in this fashion, almost like a highrise - but below ground (a lowrise?).  Mining engineers may sometimes provide additional structural support to the roof and pillars where necessary.  One drawback of this technique is that up to 50% of the economical mineral must remain as structural support. However, the structural ore can be removed near the end of mine life.  Ultimately, the ore may be recovered should the operators turn to strip mining methods later on at the property to recover all economical minerals as ore and waste heaps left behind.

 

Shrinkage Stoping

Large stopes are created in mine body when miners access the ore through a subdrift that carves out the ceiling. Large amounts of broken ore are allowed to fall to the floor and remain in the stope until the stope is complete.  The stope is then allowed to collapse.

 

Cut and Fill

SX-EW extraction

 

Infrastructure Design

Roads, workings, impoundments, dams, ventilation

Shafts, drainage tunnels, refuse banks, dumps, stockpiles, overburden piles, spoil banks,

Tailings, holes or depressions, structures, or facilities).

 

Terms and Definitions

On a hardrock (lode) mine, you enter the horizontal opening which is called an adit.

 

Shafts run vertically.  Those traveling up are called a raise while those traveling down are called a winze. Typically a winze does not open up to the surface, but instead leads to another level of the mine.

 

An 'Inn Tunnel' is a horizontal adit (sometimes called a “qanat”) constructed specifically to intercept and collect unconfined groundwater, perhaps seeping from underlying alluvium.

 

Stopes provide the primary access by miners to ore.

 

Mine Plan Summary

As with other ‘forward looking statements’ governed by regulators, the mine plan may contain a ‘Safe Harbour Statement’ explaining the applicable technical caveats and all expected risk factors that may impact expected mine life quality, quantity and economic return

 

Processing

Processing costs are more expensive than extraction costs

Sulphides are more expensive than oxides.

Oxides can be leached.

Sulphides must be crushed then roasted before milling.

 

 

7.0    General Mine Design

 

Acid Mine Drainage Treatability Studies and Plant Design

Hydrologic Investigations and Predictive Studies

Water Resource Inventories

Cost of Compliance Determinations Refuse Disposal and Waste Management Planning

Preparedness, Prevention, and Contingency Planning

Post-mining Land Use Planning

Mining Laws and Regulations

Mine Subsidence Planning and Mine Subsidence Control

 

 

 

VI.     PRODUCTION: Mining Extraction/Recovery

 

Aggregate Removal

Surface vs. Underground

 

Underground Hard Rock Mining

Install additional adits, stopes and winzes

 

Surface Mining (Open Pit)

 

Open Pit Surface mining is the most common mining technique in North American resource extraction.  Although most open pit mine development methods are the same, the actual extraction process will vary from mine to mine depending upon the geologic, geographic, and logistic particulars.

 

Capital Cost Summary

Mining Pre-production

Plant and Infrastructure
Socio-Economics
Operating Costs
 
 
Example Operating Cost Summary       Cost Percentage
Mining                                       20.3%
Environmental/Reclamation    0.7%.
Processing                               28.3%.
 

1.  Surface drilling

2.  Blasting

3.  Loading

4.  Hauling

5. Separation, Grinding, Milling, and Sizing

6.  Processing

7.  Milling

8.  Smelting

9.  Refining

 
Administration           1.0%..
Total (milled)             50.3%.

 

 

Processing

 

1.  Surface drilling

 

Overburden Removal is the use of large equipment to move massive amounts of material on the surface of topsoil and unconsolidated soil.

 

2.  Blasting

 

Once  topsoil and unconsolidated soil are cleared, explosive charges are placed on the cleared land to break up the underlying consolidated material (bedrock).  Back in the old days miners used dynamite to do this.  In modern time These blasts are electronically controlled explosions of plastic explosives.

 

3.  Loading and Mucking

 

Once the blasts occur, the ore and waste rock (muck) are cleared with heavy equipment (dozers and loaders) to facilitate removal from the development zone to the production zone.  This process is known as mucking. (Mucking also occurs in hardrock mining underground)

 

As the aggregate ore is removed and pulled back and the open pit grows larger, a series of cutbacks known as benches are established.  These benches then form the platform for building roads and infrastructure to continue mining on the next level down.

 

4.  Hauling and Primary Crushing

Heavy equipment or a series of conveyance systems moves blasted material to the crusher.  The primary crusher reduced aggregate size so that the ore may be more economically transported to the mill via additional conveyance systems, pipelines, trucks or rail lines.

 

5.  Separation, Grinding, Milling, and Sizing

 

Separation

Separate ore from topsoil (topsoil used in reclamation process)

Stockpile ore at processing plant

Convey and lime ore

Crush ore (jaw crusher, cone crusher)

 

Grinding (ball grinder). 

After ore is crushed it is fed into a very large metal container that contains steel balls.  When the grinder is rotated, the ore is ground into a finer aggregate by getting pummeled by the balls against the metal sides of the grinder.

 

Run ore into semi-autogenous grinding machine (SAG)

Remove large rocks

Pump remaining slurry (small rock @ 70microns) through trommel to sump

Run slurry through primary and secondary hydrocyclone

Regrind large rock at SAG mill 

Dispose waste ore material, known as gangue

Beneficiation – leaching, milling and recovery)

 

Processing

 

Operation Costs:

Royalty payments, refining costs, mining costs, milling costs, reclamation costs, direct and indirect operating expenses

 

Direct Operating Expenses

Mining costs,

Milling costs,

            Processing, smelting, and refining costs,

 

Labor 50-60% of all mining costs

Power 30% of all mining costs

Water

 

Indirect Operating Costs

Reclamation costs

Royalty payments

Accretion expense (operation shutdowns)

Depreciation and amortization

Loss from continuing operations

Loss from discontinued operations

Exploration and Business Development

Interest Income and expense

Foreign exchange loss and gain

Environmental Compliance

Reclamation and Severance

 

Administrative Expenses

Legal

Accounting

Stock based compensation

 

Leaching and Absorption

 

Traditionally cyanide leaching was done in vats and precipitation used zinc boxes.

 

The miner develops slurry (slurry of gold ore, carbon granules and cyanide) through carbon-in-leach and/or carbon-in-pulp process.

For copper, Solvent extraction (SXEW) is a type of heap leaching and subsequent processing used to treat secondary copper ores.

Ore/lime slurry is then moved to series of tanks where sodium cyanide solution is added.  The miner move the slurry through series of carbon absorption tanks. (Remove gold from the solution).  A that point, they 'wash' gold with superheated water (called pregnant eluate).

 

In-Situ Leaching (ISL)

 

This article does a great job explaining in-situ leachate process as used in Australia, for uranium mining. 

 

http://www.aph.gov.au/library/pubs/rp/1997-98/98rp12.htm#TECH

 

 

Processing Sulfides using a BIOX circuit.

 

For an example of an operating BIOX circuit, we look at the Golden Star production system at it’s Bogoso/Prestea project.  The main construction components include:

 

a. Completion of a Fuller Traylor gyratory crusher, associated conveyors, crushed ore stockpile and reclaim system

 

b. Construction of CIL tanks are currently

 

c. Install blower system for BIOX tanks.

 

d. Install grinding and classification section

 

e. Build Cooling tower and flotation circuit

 

f. Build and install BIOX® tanks, neutralization tanks and thickener towers

 

7.  Milling

 

Mineral Processing – Smelting and Refining

 

8.  Smelting

 

 

9.  Refining

 

Move pregnant eluate through series of stainless steel cells containing cathodes

(gold attaches to cathodes).

 

Roasting: Put yielded sludge into drying furnace (1200 degrees C). Treating ore by heat or oxygen-enriched air can remove sulfur, carbon, antimony, arsenic and other impurities.

 

Remove metal, pour into bar moulds, remove dore (80-90% pure)

Send to refinery to increase bar purity

 

Gold Reduction with Aqua Regia (1:4 ratio HNO and HCl.

 

Via Shor method

http://shorinternational.com/goldrecovery.htm

 

Next step: Transport to the Smelter.

 

Smelter Treatment

 

 

SURFACE MINING (Strip Mining)

 

Phosphate mining is primarily accomplished through strip mining. 

 

1. Overburden Removal

Horizontal near surface removal or ore and waste rock.

 

2. Excavation and Extraction

Ore and waste rock is removed from surface excavations using heavy equipment such as draglines or front-end loaders. 

Mining proceeds in a linear fashion, showing large rows or strips of mined earth - hence the name 'strip mining'.

 

3. Primary Crushing

 

4. Ore Transport

Some mines transport phosphate as a slurry through above ground pipelines to the processing mill.  However, more conventional means of transport (trucks or rail) are used most often.

 

SOLUTION MINING

 

 

VII.    ENVIRONMENTAL, PERMITTING and RECLAMATION

 

Mine operators must receive a series of permits to begin production. Once production begins the operators must meet a host of regulatory requirements and keep their production within environmental parameters specified by the permits.  Environmental responsibility provides a pillar of mine operations. Many mines are shut down by regulators - often forced by community action - or at least face some type of administrative of legal actions and sanctions, for violating environmental requirements.  All waste rock and water generated by mining operations also presents a series of environmental management issues. Finally, mining operators reclaim the lands to provide value for future generations by minimizing permanent land scarring, contaminated water runoff, or other negative lasting impacts

 

The reality on the ground is that most potentially productive mine lands, at least in N. America, have been worked over - or at least prospected - before. That results in potential liability left from the last site operator who may have left behind toxic waste, hazardous materials, polluted groundwater or created other environmental issues. Since most environmental liability is joint and several - meaning the regulators will go after both the present an previous owners of the property, regardless of who actually created the mess.  Therefore, the first environmental stage begins where the last operation left off. 

 

Due Diligence Property Assessments for Acquisition and Investment

Environmental Site Assessment, Phase I, II and III. These investigation documents are governed by American Society of Testing Materials (ASTM) standards.  Environmental firms hire a Registered Environmental Assessor to conduct the Phase I surveys to look for Recognizable Environmental Conditions and other matters of concern.  Recognizable Environmental Conditions typically include structural lead and asbestos, poly-chlorinated biphenyls (PCBs) left in old transformers, and abandoned and leaking underground storage fuel tanks.  Other matters of concern could include improperly abandoned leach pads, mercury balls, acid-mine runoff and the like.  

 

Environmental Liabilities and Risk Assessments

 

 

 

PERMITTING

 

Nevada Department of Environmental Protection

 

Mine Permit based on:

- Conceptual mine plan OR an engineered design stage, AND

- Inferred Resource Report

The Mine plan is best served with concurrent development of environmental studies since the Mining Permit is actually a series of permits, licenses, and notices:

 

  • Annual Permit

  • Air Quality Permit

  • Exploration License

  • Notice of Intent (NOI)

            Example NOI

 

A Notice of Intent may allow a miner to take a 1000-ton bulk sample and commission those workings (bypass tunnel/decline, etc.) necessary to process and extract ore deposits.  NOIs require the miner put up a bond.

  • Water Pollution Control Permit

  • Storm Water Discharge Permit.

  • Permitting efforts for a larger mill and underground mine including:

- Plan of Operations and gathering base line information for the Environmental Assessment

- Reclamation Plan/Permit (not transferable?)

- Reclamation Bond must be replaced via new bond, interim bond, or satisfied via reclamation.

- Three year review by Bureau of Land Management and NV Department of Environmental Protection

 

ENVIRONMENTAL OPERATIONS

 

I.  Environmental Management

 

1. Pollution Prevention

  • Waste Reduction

  • Prevent impacts through administrative and engineering controls before they occur.

  • Reduce toxic wastes (both quantity and quality) at the source

  • Re-use of input materials

  • Reduce, Reuse, Recycle, RE-think

Hierarchy of Pollution Pollution

 

Reduction

If you can reduce, or better yet, eliminate the hazard or source of pollution at the outset of planning and design, there is no need to manage/plan/abate/respond/remediate the hazard and its negative effects on operations, personnel, and environment when things go wrong at a later date (and they often do go wrong!).  Hence, reduction of waste/impact is the first step in pollution prevention. Pollution Prevention Opportunity Assessments, conducted by environmental specialists or consultants, are one way to begin this process. 

 

Pollution Prevention (P2) Assessments are relatively simple, though comprehensive analysis of all mine processes and operations and identification of controls that could be implemented to reduce environmental impact, resources use, and regulatory burden.  A simple PS assessment might involve:

  • Focus on a process

  • Determine energy, material and water inputs

  • Determine existing waste stream

  • Examine available research, literature and resources specific to the process and waste stream

Australian Mining Research Collaboration

 

The mining sector appears grossly undercapitalized.  Not sure I see a fundamental vision how the industry will meet the energy, transportation, social and environmental problems roiling beneath the surface.  At least a few are posing inquiries into strategies and approaches for the next few decades:
http://www.amira.com.au/?section=about&page=top

 

Then again, maybe we just stop mining for 20-30 years or so, and see what happens.

  • Determine best practicable (benefit/cost analysis) opportunity for reduction, substitution and elimination

  • Select options

  • Develop implementation workplan

  • Execute workplan

  • Re-evaluate and Re-think options upon change  in process and introduction of new materials, equipment or personnel into process

Specific examples of pollution prevention practiced by mine operations include:

  • Watering down open pits to reduce soil erosion by wind

  • Sitting Waste piles away from water bodies/eliminating potential to contaminated groundwater sources

  • Proper storage, handling, use, transportation and disposal of hazardous materials and wastes.

  • Isolating acid-producing waste rock and preventing release of acid-drainage

  • Use of drip rather than spray leaching

  • Use of scrubbers on stacks to reduce air emissions.

  • Support of local community environmental projects

 

Prevention

By substituting a less toxic material for a more toxic one, the operation can lower the overall potential negative effect to human health and the environment.  Product substitution when combined with process controls and capital improvements make for synergistic environmental controls that save money and time in the long run but require capital expenditure upfront.

 

Reuse/Recycle

  • Reuse conveyance piping

  • Reuse non-acid producing waste rock for hillside stabilization or bank stabilization (rip-rap)

  • Reuse solvents (where not reduced through substitution of bio-based products, citrus-based products and enzymes).

  • Reuse mine water for maintenance purposes, in the beneficiation process, or for habitat (wetland) restoration and maintenance

  • Process tailings

  • Recycle scrap metal

 

Reclaim

 

Leave the site a little better than you found it by providing habitat for returning species, taking away all the junk (even if it isn't yours) and providing some social and economic benefit tot he local community and stakeholders.

 

RE-Think

The most important one of all.  Follow the precautionary principle. An ounce of prevention still buys more than a pound of cure, especially when inflation-adjusted for today's rates.

 

Australian Sustainability in Industry Site:

http://www.deh.gov.au/industry/industry-performance/minerals/booklets/

 

2. Spill Prevention and Control

 

Fuels

 

Fuel storage is governed by the Spill Prevention Control and Countermeasure (SPCC) provisions of the federal Clean Water Act (CWA) and portions of the Resource Conservation and Recovery Act (RCRA).  Preventing spills and releases through use of secondary containment on fuel tanks and doubled walled tanks with emergency notification and alarm systems is much cheaper than containing and remediating fuel spills after they occur.  A program of regular inspection and response ensures consistent and ongoing spill prevention.  Fuel spills can be minimized by proper planning, design and engineering of fueling systems. For example, a fuel needs analysis may show that less fuel is required than originally envisioned. A 5,000 gallon fuel tank is easier to manage, and less costly to maintain, operate and especially - cleanup - then a 10,000 gallon tank when spills do occur.

 

Chemical Management

 

Every mine, as in all other industries, uses the beauty of chemicals to increase efficiency. The trick is wise and beneficial use that eliminates worker safety issues and environmental degradation.  Mine operators, or their environmental consultant, develop chemical management plans to effect this process.  Mining operators store supplies of reagents, dyes, petroleum, lubricants, solvents and other chemicals necessary to run a modern mining operation and maintain all the associated equipment.  Improper release of these chemicals into the environment may have deleterious effect on vegetation and wildlife and even the company's bottom line if the state of federal EPA assigns fines.  Safety issues are always a critical minder in mining operations.  Proper labeling, storage (secondary containment, use of alarms, protection from hazards and the elements) and handling (using proper equipment) of hazardous chemicals can dramatically reduce incidents and accidents.

 

Mining has historically relied on powerful chemicals - and hence potentially dangerous ones when misused - to process ore. Cyanide and mercury are just two chemicals falling under this category.

 

Cyanide

 

In  base metal processing, cyanide helps depress Iron Pyrite (Fe2) in flotation circuits.  For over a century the industry has used cyanide to separate gold from ore.  Hence, not only does cyanide use, storage and transportation pose potential problems, so does the cleanup of historical cyanide spills, dumps and tailings.  Use of cyanide (especially sodium cyanide [NaCN]  in heap leaching became economically productive in the 1970's and dramatically increases the amount of cyanide used in mining production.  Tailings ponds and solution retention basins occasionally fail through undermining - where clay, polymer or geotextile linings release cyanide solutions into the environment over time, unnoticed yet steady.  Of course, catastrophic failure also can occur due to improper engineering or natural or main-made (accident) disasters.

 

Cyanide tailings ponds and retention basins have occasionally attracted migrating waterfowl, especially on N. America flight routes, leading to both acute and chronic poisoning deaths.  Some mining operations have resorted to putting out fake bird predators, using high-pitched bird alarms and even installing nets across the tailing ponds.

 

Miners use a variety of chemicals during day to day mine operations. Acids and bases provide efficient means of managing the ore, water and waste streams. Solvents are used to clean vehicles, lubricants and oils run vehicles and equipment, and hydrocarbons make it all go.  After the product is used, then it becomes a waste which also needs proper handling storage hauling and disposal.  Release of even minor amounts of these materials and wastes into the environment can cause human health ecological problems.  Just a minute release of oil will cause a sheen on water bodies.  Cleaning up and managing these releases prove even more expensive and time intensive than purchasing and managing the chemicals in the first place.

 

3.  Natural and Cultural Resource Management

 

Through careful environmental planning and mitigation, conservation of resources, and being a good steward of the underlying environmental fabric the mining operation will actually increase profits and reduce unnecessary outlay.  

 

Habitat Modification and Taking

 

Habitat is that biological component of the underlying environmental fabric - the ecosystem which supports life.  Generally, habitat refers to three major components:

1. Aquatic (lakes, streams, rivers and other surface water features);

2. Terrestrial (vegetation that serves as cover and nesting areas and geology/soils and air); and in between, the

3. Wetlands (and dependent vegetation types)

Disturbing land, including the removal of vegetation ,also removes habitat and food sources for local creatures.  Additionally, disturbed land is usually colonized first by non-native exotic species which become established and begin to change the ecosystem type. This creates new patterns of vegetation and animal habitat.  Removal of vegetation also removes arras where animals and birds find forage, shelter, and rearing grounds. Erosion from disturbed areas runs into surface waters and causes sedimentation. In turn sedimentation can reduce available oxygen and increase turbidity which reduces available food supply and impacts aquatic life.  Aquatic organisms are noted as indicator species. That is, if their population health is not good, that indicates the entire ecosystem may be stressed. Organisms that depend upon aquatic life for food will also suffer as their food supply declines. 

 

Mitigation Measures

Maintaining, reclaiming, and revegetating mined areas provides the best opportunities to maintain and restore ecosystems that are being and have been mined. Since reclamation has an uncertainty (the vegetation may not grow back to pre-mined conditions (as is usually the case to some degree) the best mitigation measure is to maintain the environmental conditions in as good as a condition  possible while mining operations continued. Preventative maintenance goes a long way in many endeavors, including environmental management.

 

Vegetation 

 

Vegetation buffers provide a variety of highly beneficial ecosystem processes. They serve as stormwater biofilters which capture erosion runoff and therefore reduce deposition into streams. This in turn keeps the oxygen high,    Vegetation buffers also functions as an ecotone, the area between ecosystem types, and as such offer highly diverse fauna and biota. Vegetation reduces erosion and resulting sedimentation that

 

4.  Power and Water Conservation

 

Mining operations often demand large quantities of water. Water quality and quantity are directly related. The more water that is removed form  a surface body means that all the sediment, metals, and contaminants are more concentrated in the remaining water. In particular, beneficiation, demands incredible amounts of water and causes many of the negative impacts on water sources associated with any mining operation.  Making water conservation a priority during the design stage can help achieve significant water reduction during the operation stages, reducing the amount of water recirculation, recycling, and ultimately - withdraw needed to support the mine.  Tailing ponds can recycle water back to the top of the headworks and used to recirculated through the beneficiation process. Proper installation of earthen and geotechnical liners under ponds and piles will reduce the potential impact to underlying groundwater resources. 

 

Much mining in north America takes place in very dry areas where the only available water ins groundwater. Removal of groundwater can cause land subsidence.  Release of contaminants into groundwater sources prove especially troublesome as cleaning up contaminated groundwater, which often serves as a drinking water supply in rural areas, is very costly and takes a very long time in most cases.  Pit design also provides a great opportunity to reduce potential hydrologic impacts at the project beginning. The mine pit often draws in water into the bottom of the pit. This water either must be dewatered or controlled to allow continues mining. After mining operations stop, the wate5r collected in the bottom of the pit will leach out metals from the host rock, in contact with the water, and could turn good groundwater into a possible remediation problem.

 

 

5.  Air Quality

Just as mining operation may impact soil and water, so too air media.

 

Fugitive Dust Emissions are created through handling and processing ore in all stages such as ground disturbance, conveyance with machinery and equipment, loading, blasting and mucking. The development and use of the transportation system creates a large percentage of dust emissions as vehicles stir up dry particles into the air from unpaved roads.

 

Air pollution typically comprises organic and non organic material that creates potential health hazards.  Some fugitive dust may contain unhealthy levels of heavy materials or organic contaminants. Other concerns regard the size of the particulates. Very small dust particles, called particulate matter, is measured as microns across the diameter (Pm2.5, Pm10 etc.). These very small particles can create health hazards since they are small enough to evade capture of the hairs (cilia) lining your throat and end up lodged in your lungs where they then may create or exacerbate respiratory  issues. Fugitive dust also has the potential for multi media transport, where it settles out of the air into surface water bodies, in some cases many miles away, and increase water turbidity.

 

The major mitigating measures used to prevent or control fugitive dust emissions include spraying water from a tender truck to wet down exposed surfaces and prevent wind or vehicles erosion.  Operators can deposit mulch or straw or even rock on non-working surfaces to reduce wind erosion potential. Long term measures typically concentrate on reclamation which establishes new vegetation which anchors the soil in place. 

 

III.  Waste Rock and Spent Ore Management

 

 

Waste Rock

 

Waste rock, often called overburden, is uneconomic ore and other soil and rock material overlying economic ore. Miner operators must remove this waste rock to access economic ore.  Miners deposit waste rock down gradient and nearby the extraction location in waste piles or 'dumps'.   Over time, as mining and beneficiation procedures improve, these waste rock piles may become economic.  Rock considered waste 100 years ago may well produce economic grades today.

 

Mine operators have consistently developed improved management of waste rock. Originally the waste rock was piled.  Waste rock is piles or dumps can grow to hundreds of feet high and cover hundreds of acres.  Miners than began putting waste rock down stopes that were no longer of use.  Today, depending upon the physical and chemical characteristics of the waste rock, miners can use the rock as aggregate fro access and haulage roads, stream stabilization (rip-rap) and for surface impoundments.

 

Spent Ore

 

Miners move spent ore from the leach pad to the final storage/disposal location in a process called off-loading.  The final storage/disposal locations may be a depression, ravine or valley that the operator is filing in - leveling the topography - with spent ore and mine wastes.  Other disposal areas include areas of the open-pit mine that are completely played out or waste pits - including areas specifically designed to accept tailings and spent ore that might have acid runoff or other discharges which might affect water quality.

 

Operators can line these disposal areas to make them impermeable by laying down various layers of gravel, diatomaceous earth, and geotextile membranes which eliminate, reduce or control infiltration to groundwater.   Additionally, the operator may pre-treat the spent ores and waste rock before disposal in a process called detoxification [US EPA, Hard Rock Mining Program, 1997]. Often this process is conducted on the leach pad to enhance final leachate and extract all remaining economic metals before declaring the product as a waste.  Detoxification is often conducted to raise the pH of acidic rock toward neutral (ph = 7.0), or as close as possible.

 

As methods of detoxification miners may utilize fresh water, recirculated and untreated process water or hydrogen peroxide. Also, an operator may use alkaline chlorination or biological or enzyme solution treatment.

 

Miners typically extract all the economic minerals possible from an ore. The remaining uneconomical ore, or processed ore, is called spent ore.  Since the spent ore will always posses some level of the targeted ore metal (in addition to other metals present), this spent ore may present similar environmental threats as the waste rock or mill tailings, and hence benefit from many of the same preventative management techniques.  Other potential environmental issues are sulfides - which contribute to acid water discharge, and non-economical metals present such as selenium or mercury.  Since this ore has already been processed, the size is usually between gravel and pebble.  Spent ore will also have process solution present - such as cyanide (or remaining arsenic or mercury from the old days) and the by-products of those treatment materials. Operators typically to process spent ore in place, but will occasionally move them to dedicated waste dumps or no longer active portions of the open pit.

 

3. Operation Compliance Audits

 

 

III.  Mill Tailings

 

Mill tailings are the remaining materials after beneficiation. Tailing, both fine and course, are waste materials that have already had economic metals and minerals removed from the ore and now require management in order to prevent environmental degradation or interfere with mine operations.

 

Mill tailings, like waste rock and spent ore, can leach into groundwater and cause negative water quality changes. One way to prevent this is to break the portion of the hydrologic cycle which comes into contact with the mill tailings.  For example, placing a non-permeable barrier on top of the tailings (spoilings) pile will prevent rain from contacting the waste rock.  Another technique is to build a pad with an impermeable layer, such as geotextile fabric or clay (or both) and then placing the waste rock on top of this barrier. This prevents runoff from the waste pile from infiltrating into the soil and then coming in contact with groundwater.

 

The parent material, or ore, determine the physical and chemical characteristics of the tailings.  physical and chemical characteristics include pH, leach ability constant, mineral content, color, plasticity, particle size, ability to compact, etc. In turn, these characteristics drive the probability and degree to which the tailings may leach contaminants into surface or groundwaters.

 

Tailings exit the milling process as a slurry, generally one-third solids and two-thirds water. The solids at this are point are small, basically clay and sand size with some pebble-sized aggregate mixed in. The slurry produced is the waste product of ore beneficiation and metal recovery; its chemistry reflects both the host ore and the beneficiation process(es) used.

 

The tailings exit the mill and are then typically deposits, through pipes via gravity, into an impoundment. Impoundments are constructed with impermeable layers so that the as the tailings eventually de-water through evaporation, additional water does not in the meantime infiltrate through the soil into groundwater.  Impoundments are either created entirely or partially from existing topography to create a dam such as side-valley or cross-valley impoundments.  Other impoundments entirely created include designed pits or elevated berm-ring dike.

 

Leaking impoundments pose a two-fold threat. First, leaking impoundment may undermine the structure integrity of the impoundment basin - potentially leading to catastrophic failure. Secondly, leaking tailing water may impact underlying aquifer or down-gradient surface waters.

 

In some cases, especially in areas where land is at a premium - such as steep hillsides or canyons, the tailings are dewatered and dispose of in a pile called dry tailing disposal. This eliminates the need for impoundment reclamation, but increases process time and cost.  Dry tailings are often used to fill in side canyons or draws to level out topography and secure piles out of the operation area.

 

Tailing Dam Safety

http://www.wise-uranium.org/mdas.html

 

Tailing Dam Closure in the EU

http://www.clotadam.com/

 

IV.  Mine and Process Waters

 

Generally, mine water is the entire flow through a mining property, both below and above ground.  Mine water can basically be separated into those waters that runoff the surface or infiltrate into the earth versus those waters used in the production and beneficiation stages, known as process waters.  Mine water can wreak havoc on an operation for reasons of both quality and quantity. 

 

Mine Water

 

Water enters a mine either through percolation through the soil and via fractures in the bedrock, or through adits and other entrances into the mine.  The quantity of water in an underground mine will determine how much needs to be pumped out.  This in turn impacts production costs.  There are a number of mines that have great ore remaining but cannot be worked because the amount of water in the shafts makes removal uneconomic.  The Comstock Lode provides a great example. In fact, Adolphus Sutro made a name (and a fortune) for himself by completing a tunnel that de-watered the Comstock and allowed production to continue in the mines.  The depths of these mines created hot water (and remember, the Comstock Lode is only 18 miles from a major geothermal source at Steamboat), another in a long list of factors that made mining physically uncomfortable.  

 

Mining engineers will drawdown the groundwater in underground ore areas in order to better access economic deposits, a process called dewatering.  Dewatering can have environmental impacts on water resources down gradient of the mine, and the Aquatic organisms that depend on that groundwater - which may express as surface water and wetlands down-gradient.

 

The quality of water running over mine tailings, waste ore, and direct precipitation into tailings ponds and on heap leach pads create environmental quality problems that mine engineers and environmental scientists must manage. Though not an insurmountable problem, this situation adds costs to production.  Mine water reflects the parent ore body and local geological and hydrological properties.

 

Additives such as cyanide introduced into the beneficiation process, turbidity, temperature, pH, metals, and other characteristics of the host rock that have been concentrated via the mining process pose potential environmental issues if not addressed before release, or must be mitigated during and after release to the environment.

 

Acid Drainage

 

Liquid effluent that becomes acidic through oxidation of Pyrite (FeS) and other metal sulfides. Release of these metals into the environment is one primary source of acid water runoff.    Exposure of dissolved iron released from mill or tailing stockpiles or from adits to oxygen releases precipitates which lead to acidic water (pH below 7) which can then runoff into nearby waters.  FeS releases cause the yellow-red water associated with acid runoff.

 

Acid mine drainage can lower pH of nearby waters and impact the health of nearby ecosystems, especially aquatic organisms and vegetations that are negatively affected by metals (especially aluminum, zinc, cadmium) at low contaminate levels.

 

Proper engineering controls and mitigation measures can be utilized to reduce the amount or acidity of the runoff and thus lessen the negative impact on surface or receiving waters. The primary strategy - reduce flow of water into the outside environment - can be met through implementation of subsurface barriers, tailings ponds, containment ponds, groundwater pumping systems, subsurface drainage systems and treatment units,

 

Proper design, such as locating pile runoff away from receiving waters or controlling runoff from the piles provides the most effective solution for reducing environmental impacts. [USEPA, Hardrock Mining Program {530-97-005], 1997]Mitigation measures are employed after engineering controls fail, since they are usually the most time consuming and expensive way to manage a potential environmental problem.

 

Hydraulic head gradients created by tailing ponds can cause groundwater mounding where local groundwater flows are altered.

 

Certain bacteria present in soil can further increase and complicate acid water production.  Use of beneficial bacteria can also control and treat environmental problems such as acid water runoff.

 

Erosion and Sedimentation

 

The soil scientists definition of soil is that it is formed in place and has the ability to support life. Erosion is where the parent rock, and the soil produced by weathering of that parent rock, is moved through gravity, water, wind, or physical methods to another location than where it originally developed in place.  Deposition is the term used to describe soil erosion deposited onto land whereas sedimentation is when the erosion deposits soil into water.

 

Factors affecting erosion rate and degree includes the type of parent rock and soil, grade/slope, amount of rain and wind, and removal - or lack of - vegetation.  Generally, mining location in the western US are within arid climates with high soil erosion potential to begin with. Loss of minerals and structure in the topsoil lost through erosion can greatly prevent future reclamation efforts.  Sedimentation into surface waters and behind check and coffer dams or other types of containment barriers pose problems than must be mitigated and managed.  Sedimentation, measured as Total Dissolved Solids TDS), into water provides a major source of surface water quality degradation throughout the world. Sedimentation decreases sunlight penetration into the water column which lowers ability for photosynthesis, clogs fish gills, and damages ability for aquatic organisms to thrive.    Additionally sedimentation may lower the biological oxygen avail be to aquatic organisms, especially benthic invertebrates and further degrade  aquatic  biology by reducing food and spawn sources.  Further sedimentation provides a transport mechanism for environmental contaminants such as heavy metals.       

 

Controlling sedimentation provides one the greatest bang-for-the-buck mitigation control measures available for both long and short term erosion. Controlling sedimentation runoff through use of storm water management Best Management Practices (BMPs) - developed in the Stormwater Pollution Prevention Plan - can prevention to mitigate sedimentation impacts on nearby water resources.  Stormwater BMPs include those technologies that will reduce soil erosion, slow the rate and force of overland water runoff, and contain filter and treat stormwater runoff before water enters surface resources. Reducing stormwater rate lowers the overland competence - the size and amount of sediment that a water body can carry.  Treating and filtering stormwater flow, use of geotextile mats, placement of filters, riprap, fence, construction of sedimentation dykes and basins, and related control measures can eliminate or at least reduce the amount of sedimentation making its way into surface water resources.

 

Subsidence

Another potential problem that mining engineers monitor and design to prevent is subsidence of land.  Land subsides when the underlying aquifer is drained, or when too many underground voids (caverns, stopes, etc.) have been developed and the land then collapses.  Parts of Texas and Oklahoma, where the Ogalala aquifer has been excessively drained, have dropped in excess of 20 feet in the last 60 years and form a great example of land subsidence on a large scale.  Mass wasting and collapse slumphing are examples of localized subsidence.

 

Generally localized subsidence produces troughs or depressions on the ground surface caused by surface erosion where water collects, causing further erosion.  In more serious localized subsidence, sinkholes form the underlying supports (columns or shorings) fail and the overlying strata collapse into the voids. Both minor and more sever subsidence can alter local hydrology, draining surface water feature such as ponds or streams which further exacerbates erosion and subsidence issues, and can itself cause a cave-in or sinkhole.  Miners can reduce the potential for erosion and subsidence issues by increasing the amount of mine water recycled through the process and thus not deposited onto the ground.

 

The likelihood and degree of subsidence relates to the geologic, soil, and hydrology conditions of the surface soils, underlying geology, and the methods of underground mining employed- especially the type and use of pillar supports.  Traditionally engineered room and pillar typically leaves enough support to prevent cave-ins. However, high extraction techniques such as pillar retreat, and especially, long wall mining, have higher chances of collapse.  Preventing collapse, subsidence and cave-ins require proper use of supports such as pillars, shoring, timbering, or replacement of tailings for most recently removed ore.

 

RECLAMATION

 

Reclamation actually begins with a good mine plan where biological, chemical, and other  environmental factors and mitigations are properly designed into mine footprint and operations.  Taking these steps to preserve good baseline environmental conditions, especially combined with a strong environmental management system and best practices employed by the mining operator greatly reduce the cost of reclamation and increases odds for early habitat renewal.

 

Preservation of topsoil, natural topography contours, wildlife corridors, and vegetation islands/buffers wherever possible will preserve ecotones (areas of great biodiversity) and faunal and floral habitat. This in turn will speed up the reclamation process since the required plant and animal communities are still present, albeit in reduced populations. Environmental scientists have figured it is much easier to convince an extant population to grow than to establish a previously extirpated (removed) population.

 

Environmental impacts depend upon ore geochemistry, process chemicals use, site topography and hydrogeology, and the success of mitigation measure and techniques implemented to prevent environmental contamination. Environmental contamination is examined as a three part cycle: source, pathways and targets.

 

Mine Reclamation Plans

Mine Closure Liability

Mining Reclamation Liability

Example Reclamation Permit

 

http://ndep.nv.gov/docs_04/nev0244_1005p.pdf

 

Reclamation Bond

Plan of Operations/Operating Permit

 

Severance

Surface and Use Occupancy - See

 

TITLE 43--PUBLIC LANDS: INTERIOR; CHAPTER II--BUREAU OF LAND MANAGEMENT,
                       DEPARTMENT OF THE INTERIOR [PART 3710--PUBLIC LAW 167; ACT OF JULY 23, 1955]

 

Abandonment

 

Introduction

 

Reclamation Factors Table:

http://www.goldinstitute.org/mining/environ.html#FISH

 

Regulatory Environment

Federal Land Policy and Management Act

National Environmental Policy Act

Clean Air Act

Clean Water Act

Comprehensive Environmental Response, Compensation and Liability Act

Emergency Planning and Community Right to Know Act

Solid Waste Disposal Act

Safe Drinking Water Act

Migratory Bird Treaty Act

Toxic Substances Control Act

Endangered Species Act

Resource Conservation and Recovery Act

Mining Law of 1872

River and Harbors Act

National Historic Preservation Act

Native American Graves Protection and Repatriation Act

Federal Mine Safety and Health Act of 1977 (Mine Act)

 

Reclamation Costs

Within the Department of Interior, the largest land management agency in the US Government, reclamation costs vary from between $2-10K/acre on BLM sites and up to $100K an acre for full restoration on National Park Service sites.

 

Surface Mining Control and Reclamation Act

 

Re-contouring

Mechanical tail pulling

Mechanical re-contouring to original slope, backfilling sumps, ripping and seeding with native weed-free mixes.

Topsoil (or equivalent substitute replacement)

Revegetation

Mechanical Hydro seeding

Helicopter Seeding

Monitoring

 

Canadian Permitting

Application Requirements for a Permit Approving the Mine Plan and Reclamation Program Pursuant to the Mines Act

 

Mining Restoration Support

 

US Metal Mine Restoration Projects

some good stuff here:
http://ecorestoration.montana.edu/mineland/histories/metal/default.htm

 

Colorado Hazardous Substance Research Center

http://www.engr.colostate.edu/hsrc/

 

VIII.   SAFETY

 

IX.  FUTURE SITE USE

Parks and Recreation (wildlife preserves, fishing, hiking, hunting, biking, golf)

Ranching Farming

Development

 

 

 

X.     MANAGEMENT, ADMINISTRATION and INVESTOR RELATIONS

 

Corporate Governance

In Canada, the provisions that govern corporate governance include:

National Instrument 58-101 (NI58-101) “Disclosure of Corporate Governance Practices)”

 

National Policy (NP 58-201) “Corporate Governance Guidelines”

 

“Canadian Securities Administrator implement guidelines on best corporate government practice, though this requirement is apparently not mandatory.”

 

In the US, the provisions that govern corporate governance include:

Listing standards of the bourse (AMEX, NYSE etc.), and

Sarbanes-Oxley Act of 2002

 

Corporate Governing Principles

Composition of Board of Directors

Committees

Position Descriptions

Director Orientation and Continuing Education

Board Function and Independence

Shareholder Communication

Code of Ethics

Whistleblower Policy

 

BOARD OF DIRECTORS

The Board of Directors sets and implements the companies mission statement.  Typical Board committees include:

 

Compensation

Environmental Health and Safety

Sustainability

Nominating and Corporate Governance

Financial Audit

 

The board typically undergoes a periodical assessment that may include:

  • Chief Officer and board member Indebtedness

  • Setting number and electing Directors

  • Conflict of Interest

  • Material Interest of Board Members in Corporate Transactions

  • Previous oversight of concerns that ceased operation

 

FINANCIAL REPORTING

 

Financial Statements

Boards Responsibility for Financial Reporting

Report of Independent Registered Chartered Accountant

Consolidated Statement of Earnings

Consolidated Balance Sheets

Consolidated Statements of Cash Flows

Consolidated Statements of Shareholders Equity

Notes to Consolidated Financial Statements

 

Environmental Liabilities

            Reporting, Reclamation, Remediation, Severance

 

Revenue Recognition

1.  Stripping

2.  Depreciation and Depletion

3.  Impairment of Log-lives Assets

4.  Third Party Transactions

5.  Risk

            Interest Rate,

            Foreign Exchange,

             Commodity Pricing

            Market Risk: Underlying price of commodity and inputs

            Financial Instruments: Hedges, forwards, contracts, and other derivatives

            National Risk

            Force Majeure and Acts of God

            Change in Officer and Principals

 

6.  Due Disclosure

7.  Changes in internal control

8.  Significant Accounting Policies

9.  Sarbanes Oxley

10.  Report of Independent and Registered Accountants (Financial Audit)

11.  Principles of Consolidation

12.  Uncertainty in measurement of reserves

13.  Foreign currency transactions

14.  Cash and equivalents

 

Restricted certificates of deposit held for site closure obligations

Guarantees by third party firms (typically insurance) where cash in placed in a trust as a security to the state where the mining takes place. This trust meets the bonding requirement of the state. The miner must meet minimal requirements specified in the bond and must pay the insurers monthly installments until the balance in the trust account equal to the penal sum on the bond entered into by the miner.  Monthly payment are often adjusted periodically to reflect underlying commodity prices.

 

Restricted certificates of deposit held as convertible debentures

Similar to the process for restricted CDs. In Canada, the Canada Trust Company holds the security within trusts.

 

15.  Inventories

            Concentrate, Dore, Materials and supplies

16.  Property, plant and equipment

            Mine assets (buildings, plant and equipment = ‘book value’)

            Mining properties

            Development costs

17.  Mineral Rights

18.  Stripping Costs

19.  Exploration Expenditures

20.  Property Evaluations

21.  Convertible Debentures

22.  Notes Payable

23.  Employee Benefit Plan

24.  Accrued Site Closure Costs

25.  Reclamation and Closure Costs

26.  Revenue Recognition

27.  Commodity Contracts

28.  Stock Incentive Plans

29.  Foreign Country Risk

30.  Loss per share

31.  Share Capital

Shares issues in current reporting period

Shares issues in previous reporting period

Warrants

Options

Stock based compensation

32.  Income Tax

33.  Commitments and Contingencies

            Royalties

            Litigation

            Environmental

            Indemnification obligations

            Change in sales

34.  Lease commitments

35.  Financial Derivatives and Instruments

36.  Material Change in laws, regulations and authorities

37.  Comparative figures (re-statement of previous reporting periods)

 

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