InsideMetalsฎ  |  Milling | Heap Leaching | Mining Glossary

 


 

Agitation – In metallurgy, the act or state of being stirred or shaken mechanically, sometimes accomplished by the introduction of compressed air.

 

Anode – A rectangular metal plate with positive charge cast in a shape suitable for refining by the electrolytic process.

 

Assay – A chemical test by wet or fire methods performed on a rock sample to determine the amount of valuable metal contained.

 

Autogenous Grinding – The process of grinding ore with ore in a rotating cylindrical mill using large pieces of ore instead of steel rods or balls.

 

Ball Mill – A steel cylinder containing about 40% volume of steel balls used to grind ore.  The mill is rotated causing the balls to cascade and grind the ore.

 

Beneficiation – The concentrating or enriching of the valuable minerals in an ore.

 

Bio-Leaching – A processing method that uses bacteria to oxidize refractory sulfide ore to make it amenable to normal oxide ore processing techniques.

 

Block Caving – An inexpensive method of underground mining in which large blocks or ore are undercut, causing the ore to break or cave under its own weight.

 

Bond – An agreement to pay a certain amount of interest over a given period of time.  A bond may be required to ensure reclamation of a mine site.

 

Bullion – Metal formed into bars or ingots.

 

Calcine – Concentrate ready for smelting; the sulfur has been driven off by oxidation.

 

Call Option – An option which gives the holder the right but not the obligation to purchase a stated quantity of gold ounces or other metal at a specified price on or before a given date.

 

Capitalization – A financial term used to describe the value financial markets put on a company; determined by multiplying the number of outstanding shares of a company by the current stock price.

 

Capital Stock – The total ownership of a limited liability company divided among a specified number of shares.

 

Carbon – Fine sized granules of activated carbon, typically ground coconut shell because of its hardness.

 

Carbon-in-Column (CIC) – A method of recovering gold and silver from pregnant solution from the heap leaching process by adsorption of the precious metals onto fine carbon suspended by up-flow of solution through a tank.

 

Carbon-in-Leach (CIL) - A method of recovering gold and silver from fine ground ore by simultaneous dissolution and adsorption of the precious metals onto fine carbon in an agitated tank of ore solids/solution slurry.  The carbon flows counter currently to the head of the leaching circuit.

 

Carbon-in-Pulp CIP)  – A method of recovering gold and silver from fine ground ore by adsorption of the precious metals onto fine carbon in an agitated tank of ore solids/solution slurry.  This recovery step in the process follows the leaching process which is done in similarly agitated tanks, but without contained carbon.

 

Cash Flow – The net of the inflow and outflow of cash during an accounting period.  Does not account for depreciation or bookkeeping write-offs which do not involve an actual cash outlay.

 

Cash Operating Costs, Total Cash Costs and Total Production Costs are non-GAAP measures and are calculated in accordance with gold industry guidelines and used by management to assess performance of individual operations:

 

Cash Operating Cost – Cost per ounce that is equivalent to direct operating expense, including mining and processing, waste stripping and minesite G&A, less production royalties, mining taxes and by-product credits for payable metals recovered.

 

Total Cash Cost –  Cash Operating Cost plus production royalties and mining taxes.

 

Total Production Cost – Total Cash Cost plus depreciation and amortization.

 

Cathode – A rectangular metal plate with a negative charge used in electrolytic refining.  The deposited metal recovered onto this plate is called cathode metal and is melted into commercial shapes such as bars or ingots.

 

Clarifier Filter – A pressure filter containing cloth leaves which support a porous filter medium and filter out all fine solids from relatively clear feed solution.  The sludge collected is periodically flushed from the filter on a regular cycle.

 

Classifier – A mineral processing machine which separates mineral particles according to size and density.

 

Common stock – Shares in a company which have full voting rights which the holders use to control the company in common with each other.  There is no fixed or assured dividend as with preferred shares, which have first claim on the distribution of a company’s earnings or assets.

 

Complex Ore – An ore containing a number of minerals of economic value.  The term implies that there are metallurgical difficulties in liberating and separating the valuable minerals.

 

Cone Crusher – A machine which crushes ore between a gyrating cone or crushing head and an inverted, truncated cone known as a bowl.

 

Concentrate – A fine product separated in the milling process that contains a high percentage of valuable metal.

 

Concentrator – A milling plant that produces a concentrate of the valuable minerals or metals.  Further treatment is required to recover the pure metal.

 

Conveyor – A rubber reinforced continuous belt supported on rollers called idlers which transports solid materials between stockpiles, surge bins, and feeders.  The belt is driven by an electric drive motor at the head pulley.

 

Cut-and-Fill – A method of stoping in which ore is removed in slices, or lifts, and then the excavation is filled with rock or other waste material (backfill), before the subsequent slice is extracted.

 

Cut-Off Grade – A grade level below which the material is not “ore” and considered to be uneconomical to mine and process.  The minimum grade of ore used to establish reserves.

 

Cyanidation – A method of extracting exposed gold or silver grains from crushed or ground ore by dissolving it in a weak cyanide solution.  This may be carried out in agitated tanks in a mill or on ore heaps outside.

 

Deaeration Tower – A closed tank from which air (oxygen) is evacuated by a vacuum pump on the closed system.  As solution flows through a contained media of large surface area, oxygen is removed (boils) from the solution.

 

Derivative – A collective term for securities whose prices are based on the prices of another underlying investment.  Derivatives are essentially a bet on which way the price of the underlying instrument is going and can be used to reduce the risk of (hedge) and investment in the underlying instrument.

 

Dewatering – The process of separating solids from solution by sedimentation in tanks called thickeners or by filtering the solution through filter cloth in filters.

 

Dilution – Mixing of ore grade material with non-ore grade waste material in the mining process.

 

Dore – Unrefined gold bullion containing various impurities such as silver, copper and mercury, which will be further refined to near pure gold.

 

Due Diligence – The degree of care and caution required before making a decision.  A financial and technical investigation to determine whether an investment is sound.

 

Electrolysis – An electric current is passed through a solution containing dissolved metals causing the metals to be deposited onto the negatively charged cathode.

 

Electrolytic Refining – The process of purifying metal plates that are suspended as anodes in an electrolytic bath.  The valuable metal is plated onto refined sheets called cathodes of the same metal which act as starters.

 

Electrowinning – The removal of precious metals from solution by the passage of current through an electrowinning cell.  A direct current supply is connected to the anode and cathode.  As current passes through the cell, metal is deposited on the cathode.  When sufficient metal has been deposited on the cathode, it is removed from the cell and the sludge rinsed off the plate and dried for further treatment.

 

Feasibility Study – An engineering study designed to define the technical, economic, and legal viability of a mining project with a high degree of reliability.

 

Filter Press - A pressure filter containing cloth leaves which are supported within a closed container to remove solids from a fine solids feed slurry.  The solids sludge collected is periodically removed from the filter by opening the filter plates, scraping off the solids and replacing the plates with new and clean filter cloth or filter paper for continued filtering.

 

Flotation – A milling process in which valuable mineral particles are induced to become attached to bubbles and float away from the waste particles in a solid/solution pulp.

 

Flow-through Shares – Shares in an exploration company that allow the tax deduction or credits for mineral exploration to be passed to the investor.

 

Flux – A mix of chemical substances that react with gangue minerals to form slags, which are liquid at smelting furnace temperature and low enough in density to float on the molten bath of metal.

 

Free Milling – Ores of gold or silver from which the precious metals can be recovered by concentrating methods without resorting to pressure leaching or other chemical treatment.

 

Gangue – The worthless minerals in an ore deposit.

 

Gold Loan – A form of debt financing whereby a potential gold producer borrows gold from a lending institution, sells the gold on the open market, uses the cash for mine development, then pays back the gold from actual mine production.

 

Gold Precipitate – Fine sludge of gold, silver, and zinc.  The precious metals are precipitated out of solution by the addition of fine zinc dust.

 

Grade – The metal content of ore in Troy ounces per ton or percent.  Head grade is the average grade of ore fed into a mill or heap leach metal recovery operation.

 

Grizzly – A grating, usually constructed of steel rails, placed over the top of a chute or ore pass for the purpose of stopping large pieces of rock or ore that may hang up in the pass.

 

Gyratory Crusher – A machine that crushes ore between an eccentrically mounted crushing cone and a fixed crushing throat.  Typically, it has a higher capacity than a jaw crusher.

 

Heap Leach – A mineral processing method involving the crushing and stacking of ore on an impermeable liner upon which leach solutions are sprayed to dissolve metals such as gold and copper.  The metal, in the collected solution flowing from the leach pad is subsequently treated to recover the metals.

 

Hedging – Taking a buy or sell position in a futures market opposite to a position held in the cash market to minimize the risk of financial loss from an adverse price change.

 

Jaw Crusher – A machine in which rock is broken by the action of swinging steel plates.

 

Jig – A piece of milling equipment used to concentrate high density minerals by gravity on a screen submerged in water, either by the reciprocating motion of the screen or by the pulsation of water through it.

 

Leaching – A chemical process for the extraction of valuable minerals from ore.

 

Merrill-Crowe (M-C) Circuit – A process which recovers precious metals from solution by first clarifying the solution, then removing the air contained in the clarified solution, and then precipitating the gold and silver from the solution by injecting zinc dust into the solution.  The valuable sludge is collected in a filter press for drying and further treatment.

 

Metallurgy – The study of extracting metals from their ores.

 

Mill – A processing plant which treats ore for the purpose of upgrading the mineral content into a higher grade product called a concentrate, which is further treated, and disposing of the waste minerals to an impoundment area.

 

Metal recovery from milling operations generally ranges from 90% to 95% and is higher than from heap leaching operations which may range from 65% to 85%.  Generally, most underground mine production will be processed through a concentrator operation to allow favorable economics with high metal recovery on high grade ore.  Low grade open pit ores will be treated economically by heap leach methods.

 

Mine – An excavation from which ore or minerals are extracted.  The ore may be removed from an open pit on surface by truck haulage or from underground openings (workings) via a shaft and hoist equipment to the surface for further transport.

 

Open pit mines in precious metal and base metal operations that excavate massive orebodies are of considerable area and relief (depth) in comparison to shallow strip mining methods used in removing flat-lying mineral deposits such as coal.  The mining method used is based on the depth and grade of the ore and the over-all economics of mining and processing.

 

Mineral – A naturally occurring homogeneous substance having definite physical properties and chemical composition and usually a crystal form.

 

Mineral Resources and Mineral Reserves Definitions are as set out in the Canadian Institute of Mining, Metallurgy and Petroleum Standards on Mineral Resources and Mineral Reserves Definitions and Guidelines (the “CIM Standards”) adopted by the CIM Council on August 20, 2000:

 

Mineral Resource – a concentration or occurrence of natural, solid, inorganic or fossilized organic material in or on the Earth’s crust in such form and quantity and of such a grade or quality that it has reasonable prospects for economic extraction.  The location, quantity, grade, geological characteristics and continuity of a Mineral Resource are known, estimated or interpreted from specific geological evidence and knowledge.

 

Inferred Mineral Resource – that part of a Mineral Resource for which quantity and grade or quality can be estimated on the basis of geological evidence and limited sampling and reasonably assumed, but not verified, geological and grade continuity.  The estimate is based on limited information and sampling gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes.

 

Indicated Mineral Resource – that part of a Mineral Resource for which quantity, grade or quality, densities, shape and physical characteristics, can be estimated with a level of confidence sufficient to allow the appropriate application of technical and economic parameters, to support mine planning and evaluation of the economic viability of the deposit.  The estimate is based on detailed and reliable exploration and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough for geological and grade continuity to be reasonably assumed.

 

Measured Mineral Resource – that part of a Mineral Resource for which quantity, grade or quality, densities, shape, physical characteristics are so well established that they can be estimated with confidence sufficient to allow the appropriate application of technical and economic parameters, to support production planning and evaluation of the economic viability of the deposit.  The estimate is based on detailed and reliable exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough to confirm both geological and grade continuity.

 

Mineral Reserve – the economically mineable part of a Measured or Indicated Mineral Resource demonstrated by at least a preliminary feasibility study.  This study must include adequate information on mining, processing, metallurgical, economic and other relevant factors that demonstrate, at the time of reporting, that economic extraction can be justified.  A Mineral Reserve includes diluting materials and allowances for losses that may occur when the material is mined.

 

Probable Mineral Reserve – the economically mineable part of an Indicated, and in some circumstances a Measured Mineral Resource demonstrated by at lease a preliminary feasibility study.  This study must include adequate information on mining, processing, metallurgical, economic, and other relevant factors that demonstrate, at the time of reporting, that economic extraction can be justified.

 

Proven Mineral Reserve – the economically mineable part of a Measured Mineral Resource demonstrated by at least a preliminary feasibility study.  This study must include adequate information on mining, processing, metallurgical, economic, and other relevant factors that demonstrate, at the time of reporting, that economic extraction is justified.

 

Muck – Ore or rock that has been broken by blasting.

 

Native Metal – A metal occurring in nature in pure form, uncombined with other elements.

 

Net Smelter Return Royalty (NSR) – A defined percentage of the gross revenue from a resource extraction operation, less a proportionate share of transportation, insurance, and processing costs.

 

Non-Refractory – Ore containing gold or other metal that can be satisfactorily recovered by basic gravity concentration or simple cyanidation methods.

 

Ore – A mixture of valuable minerals and gangue minerals from which at least one of the minerals can be extracted at a profit.  An orebody is a natural concentration of valuable material that can be extracted and sold at a profit.

 

Placer – A deposit of sand and gravel containing valuable metals such as gold, tin, or diamonds.

 

Platinum Group Metals (PGM’s) – The two triads of the elements ruthenium, rhodium, palladium and osmium, iridium, platinum, are grouped together under the name platinum metals.  The platinum metals are all found native, almost always associated with each other and mixed with gold, silver, copper, nickel, and iron.

 

Put Option – A financial instrument that provides the right, but not the obligation, to sell a specified number of ounces of gold at a specified fixed price on or before a given date.

 

Reclamation – The process of returning land to another use after mining is completed.

 

Recoverable – That portion of metal contained in ore that can be extracted by processing.

 

Refining – To process material to a pure state.  Precious metal bullion is fire refined to high purity gold and silver.

 

Refractory – Gold mineralization normally requiring more sophisticated processing technology for extraction, such as roasting or autoclaving under pressure.

 

Reverberatory Furnace – A long, flat furnace used to slag gangue minerals and produce a matte of sulfide minerals.

 

Rod Mill – A rotating steel cylinder that uses steel rods as a means of grinding ore.

 

Run-of-Mine (ROM) – Mined ore of a size that can be processed without further crushing.

 

Slag – The vitreous mass of glass material separated from the fused metals in the smelting process.

 

Smelting Furnace – A furnace, usually cylindrical, used to melt concentrated valuable metals and minerals and further upgrade them by slagging off gangue minerals with the use of chemical flux materials.

 

Sodium Cyanide – A chemical used in the milling and heap leaching of gold ores to dissolve gold and silver.

 

Solutions – Various water solutions in the leaching circuit, from fresh make-up water, to pregnant solution containing significant amounts of precious metals and leaching reagents (chemicals), to barren solution which contains small quantities of valuable metals but mainly the leaching reagents.

 

Solvent Extraction-Electrowinning (SX-EW) –A metallurgical technique, so far applied only to copper ores, in which metal is dissolved from the rock by organic solvents and recovered from solution by electrolysis.

 

Stripped Carbon – Activated coconut shell carbon which has had the precious metal values removed by chemical processing in preparation for reactivation and recycling back to the stripping circuit.

 

Strip Ratio – The ratio of tons of overburden waste material to tons of ore in an open pit mine.  The waste rock removed in order to expose the orebody in an open pit mine is hauled only once to a waste disposal area, in contrast to strip mining where waste rock is replaced to reclaim the flat lying mined-out area.

 

Strip Vessel – The closed container in which loaded carbon is placed to remove (desorb) precious metals from the surface of the activated carbon.

 

Tailings – Crushed or finely ground waste rock from which valuable minerals or metals have been extracted.

 

Ton – A “short” ton measure of weight containing 2,000 pounds and equal to 0.907 Tonnes.

 

Tonne – A “metric” tonne weight measure containing 1,000 kilograms.

 

Troy Ounce – A measure of weight in which precious metals are sold.  One Troy Ounce contains 31.1 grams.  A kilogram contains 1,000 grams.

 

Vein – A fissure, fault or crack in a rock filled by minerals that have travelled upwards from a deeper source.

 

Waste – Barren rock or mineralized material that is too low in grade to be economically processed.

 

Working Capital – The liquid resources a company has to meet day-to-day expenses of operation; defined as the excess of current assets over current liabilities.

 

Zinc Dust – Fine zinc metal used to precipitate gold and silver from solution.  The precious metal values precipitate into a fine sludge and the zinc metal replaces these values in solution.

 


 

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