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Glossary of Mining Terms



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A Glossary of Some Mining Related Terms

Adit: An opening driven horizontally into the side of a mountain or hill for providing access to a mineral deposit.

Alteration: Any physical or chemical change in a rock or mineral subsequent to its formation. Milder and more localized than metamorphism.

Anticline: An arch or fold in layers of rock shaped like the crest of a wave.

Assay: A chemical test performed on a sample of ores or minerals to determine the amount of valuable metals contained.

Backfill: Waste material used to fill the void created by mining an orebody.

Ball Mill: A steel cylinder filled with steel balls into which crushed ore is fed. The ball mill is rotated, causing the balls to cascade and grind the ore.

Base Metal: Any non-precious metal (e.g. copper, lead, zinc, nickel, etc.).

Bedding: The arrangement of sedimentary rocks in layers.

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

Breccia: A rock in which angular fragments are surrounded by a mass of fine-grained minerals.

Bulk Mining: Any large-scale, mechanized method of mining involving many thousands of tons of ore being brought to surface per day.

Channel Sample: A sample composed of pieces of a vein or mineral deposit that have been cut or chipped out a small trench or channel, usually about ten cm wide and two cm deep.

Chute: An opening, usually constructed of timber and equipped with a gate, through which ore is drawn from a stope into mine cars.

Commercially Mineable Ore Body: A mineral deposit that contains ore reserves that may be mined economically.

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

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, powdery product of the milling process containing a high percentage of valuable metal.

Conglomerate: A sedimentary rock consisting of rounded, water-worn pebbles or boulders cemented into a solid mass.

Contact: A geological term used to describe the line or plane along which two different rock formations meet.

Core: The long cylindrical piece of rock, about an inch or more in diameter, brought to surface by diamond drilling.

Crosscut: A horizontal opening driven from a shaft and (or near) right angles to the strike of a vein or other orebody.

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.

Cyanidation: A method of extracting exposed gold or silver grains from crushed or ground ore by dissolving it in a weak cyanide solution. May be carried out in tanks inside a mill or in heaps of ore out of doors.

Decline: An underground passageway connecting one or more levels in a mine, providing adequate traction for heavy, self-propelled equipment. Such underground openings are often driven in an upward or downward spiral, much the same as a spiral staircase.

Development: Work carried out for the purpose of opening up a mineral deposit and making the actual ore extraction possible.

DevelopmentDrilling: Drilling to establish accurate estimates of mineral reserves.

DiamondDrill: A rotary type of rock drill that cuts a core of rock that is recovered in long cylindrical sections, two centimeters or more in diameter.

Dilution: (mining) Rock that is, by necessity, removed along with the ore in the mining process, subsequently lowering the grade of the ore.

Dip: The angle at which a vein, structure or rock bed is inclined from the horizontal as measured at right angles to the strike.

DisseminatedOre: Ore carrying small particles of valuable minerals spread more or less uniformly through the host rock.

Dore: Unparted gold and silver poured into molds when molten to form buttons or bars. Further refining is necessary to separate the gold and silver.

Drift: A horizontal underground opening that follows along the length of a vein or rock formation as opposed to a cross-cut which crosses the rock formation.

Drill-indicatedReserves: The size and quality of a potential orebody as suggested by widely spaced drill holes; more work is required before reserves can be classified as probable or proven.

DueDiligence: The degree of care and caution required before making a decision; loosely, a financial and technical investigation to determine whether an investment is sound

Environmental Impact Study: A written report, compiled prior to a production decision, that examines the effects proposed mining activities will have on the natural surroundings.

Epithermal Deposit: A mineral deposit consisting of veins and replacement bodies, usually in volcanic or sedimentary rocks, containing precious metals, or, more rarely, base metals.

Exploration: Work involved in searching for ore, usually by prospecting, geology, geophysics, geochemistry, drilling or driving a drift.

Face: The end of a drift, crosscut or stope in which work is taking place.

Fissure: An extensive crack, break or fracture in rocks.

Float: Pieces of rock that have been broken off and moved from their original location by natural forces such as gravity, frost or glacial action.

Floatation: A milling process in which valuable mineral particles are induced to become attached to bubbles and float, and others sink.

Footwall: The rock on the underside of a vein or ore structure.

Fracture: A break in the rock, the opening of which allows mineral bearing solutions to enter. A "cross-fracture" is a minor break extending at more-or-less right angles to the direction of the principal fractures.

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

Galena: Lead sulphide, the most common ore mineral of lead.

Geophysical Survey: Indirect methods of investigating the subsurface geology using the applications of physics including electric, gravimetric, magnetic, electromagnetic, seismic, and radiometric principles.

Grab Sample: A sample from a rock outcrop that is assayed to determine if valuable elements are contained in the rock. A grab sample is not intended to be representative of the deposit, and usually the best-looking material is selected.

Grade: The average assay of a ton of ore, reflecting metal content.

Hangingwall: The rock on the upper side of a vein or ore deposit.

Head Grade: The average grade of ore fed into a mill.

Heap Leaching: A process involving the percolation of a cyanide solution through crushed ore heaped on an impervious pad or base to dissolve minerals or metals out of the ore.

High Grade: Rich ore. As a verb, it refers to the selective mining of the best or highest grade ore in a mineral deposit.

Host Rock: The rock surrounding an ore deposit.

Hydro Metallurgy: The treatment of ore by wet processes (e.g., leaching) resulting in the solution of a metal and its subsequent recovery.

Intrusive: A body of igneous rock formed by the consolidation of magma intruded into other rocks, in contrast to lavas, which are extruded upon the surface.

Lagging: Planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks.

Lens: Generally used to describe a body of ore that is thick in the middle and tapers towards the ends.

Level: The horizontal openings on a working horizon in a mine; it is customary to work mines from a shaft, establishing levels at regular intervals, generally about 50 meters or more apart.

Limestone: A bedded, sedimentary deposit consisting chiefly of calcium carbonate.

Lode: A mineral deposit in solid host rock.

Metamorphic Rocks: Rocks which have undergone a change in texture or composition as the result of heat and/or pressure.

Mill: A processing plant that produces a concentrate of the valuable minerals or metals contained in an ore deposit. The concentrate must then be treated in some other type of plant, such as a smelter, to affect recovery of the pure metal.

Milling Ore: Ore that contains sufficient valuable minerals to be treated by the milling process.

Mineable Reserves: Ore reserves that are known to be extractable using a given mining plan.

Mineral: A naturally occurring homogeneous substance having definite physical properties and chemical composition and, if formed under favorable conditions, a definite crystal form.

Mineral Resource: A deposit or concentration of natural, solid, inorganic or fossilized organic substance in such quantity and at such grade or quality that extraction of the material at a profit is currently or potentially possible.

Mineralized Material or Deposit: A mineralized body which has been delineated by appropriate drilling and/or underground sampling to support a sufficient tonnage and average grade of metal(s). Under SEC standards, such a deposit does not qualify as a reserve until a comprehensive evaluation, based upon unit cost, grade, recoveries, and other factors, conclude economic feasibility.

Mineralization: The presence of economic minerals in a specific area or geological formation.

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 Profit Interest: (NPI) A portion of the profit remaining after all charges, including taxes and bookkeeping charges (such as depreciation) have been deducted.

Net Smelter Return: (NSR) A share of the net revenues generated from the sale of metals produced by a mine.

Open Pit: A mine that is entirely on surface. Also referred to as open-cut or open-cast mine.

Ore: Material that can be mined and processed at a positive cash flow.

Ore Pass: Vertical or inclined passage for the downward transfer of ore connecting a level with the hoisting shaft or a lower level.

Orebody: A natural concentration of valuable material that can be extracted and sold at a profit.

Ore Reserves: The calculated tonnage and grade of mineralization which can be extracted profitably; classified as possible, probable and proven according to the level of confidence that can be placed in the data.

Oreshoot: The portion, or length, of a vein or other structure, that carries sufficient valuable mineral to be extracted profitably.

Oxidation: A chemical reaction caused by exposure to oxygen that results in a change in the chemical composition of a mineral.

Participating Interest: A company's interest in a mine, which entitles it to a certain percentage of profits in return for putting up an equal percentage of the capital cost of the project.

Pillar: A block of solid ore or other rock left in place to structurally support the shaft, walls or roof of a mine.

Placer Claim: A mining claim located upon gravel or ground whose mineral contents are extracted or concentrated by the use of water, by panning, sluicing, hydraulicking, etc.

Placer Deposit: A deposit of sand or gravel that contains particles of gold, gemstones, or other heavy minerals of value. The common types are stream gravels and beach sands.

Placer Gold: Gold occurring in more or less coarse grains or flakes and obtainable by washing the sand, gravel, etc., in which it is found. Also called alluvial gold.

Placer Mining: The extraction of heavy minerals from a placer deposit by concentration in running water. It includes ground sluicing, panning, shoveling gravel into a sluice, scraping by power scraper and excavation by dragline, dredge or other mechanized equipment.

Porphyry: Any igneous rock in which relatively large crystals, called phenocrysts, are set in a fine- grained groundmass.

Precambrian Shield: The oldest, most stable regions of the Earth's crust, the largest of which is the Canadian Shield

Prospect: A mining property, the value of which has not been determined by exploration.

Proven and Probable Mineral Reserves: Reserves that reflect estimates of the quantities and grades of mineralized material at a mine which the Company believes could be recovered and sold at prices in excess of the cash cost of production. The estimates are based largely on current costs and on projected prices and demand for such mineralized material. Mineral reserves are stated separately for each such mine, based upon factors relevant to each mine. Proven and probable mineral reserves are based on calculations of reserves provided by the operator of a property that have been reviewed but not independently confirmed by the Company. Changes in reserves represent general indicators of the results of efforts to develop additional reserves as existing reserves are depleted through production. Grades of ore fed to process may be different from stated reserve grades because of variation in grades in areas mined from time to time, mining dilution and other factors. Reserves should not be interpreted as assurances of mine life or of the profitability of current or future operations.

Probable Reserves: Resources for which tonnage and grade and/or quality are computed primarily from information similar to that used for proven reserves, but the sites for inspection, sampling and measurement are farther apart or are otherwise less adequately spaced. The degree of assurance, although lower than that for proven reserves, is high enough to assume continuity between points of observation.

Proven Reserves: Resources for which tonnage is computed from dimensions revealed in outcrops, trenches, workings or drill holes and for which the grade and/or quality is computed from the results of detailed sampling. The sites for inspection, sampling and measurement are spaced so closely and the geologic character is so well defined that size, shape, depth and mineral content of reserves are well established. The computed tonnage and grade are judged to be accurate, within limits which are stated, and no such limit is judged to be different from the computed tonnage or grade by more than 20%.

Raise: A vertical or inclined underground working that has been excavated from the bottom upward.

Rake: The trend of an orebody along the direction of its strike.

Reclamation: The restoration of a site after mining or exploration activity is completed.

Recovery: The percentage of valuable metal in the ore that is recovered by metallurgical treatment.

Replacement Ore: Ore formed by a process during which certain minerals have passed into solution and have been carried away, while valuable minerals from the solution have been deposited in the place of those removed.

Reserves: That part of a mineral deposit which could be economically and legally extracted or produced at the time of the reserve determination. Reserves are customarily stated in terms of "Ore" when dealing with metalliferous minerals.

Resource: The calculated amount of material in a mineral deposit, based on limited drill information.

Rockbolting: The act of supporting openings in rock with steel bolts anchored in holes drilled especially for this purpose.

Rock Mechanics: The study of the mechanical properties of rocks, which includes stress conditions around mine openings and the ability of rocks and underground structures to withstand these stresses.

Room-and-Pillar Mining: A method of mining flat-lying ore deposits in which the mined-out area, or rooms, are separated by pillars of approximately the same size.

Rotary Drill: A machine that drills holes by rotating a rigid, tubular string of drill rods to which is attached a bit. Commonly used for drilling large-diameter blast holes in open pit mines.

Royalty: An amount of money paid at regular intervals by the lessee or operator of an exploration or mining property to the owner of the ground. Generally based on a certain amount per ton or a percentage of the total production or profits. Also, the fee paid for the right to use a patented process.

Sample: A small portion of rock or a mineral deposit, taken so that the metal content can be determined by assaying.

Secondary Enrichment: Enrichment of a vein or mineral deposit by minerals that have been taken into solution from one part of the vein or adjacent rocks and redeposited in another.

Shaft: A vertical or steeply inclined excavation for the purpose of opening and servicing a mine. It is usually equipped with a hoist at the top which lowers and raises a conveyance for handling personnel and materials.

Shear or Shearing: The deformation of rocks by lateral movement along numerous parallel planes, generally resulting from pressure and producing such metamorphic structures as cleavage and schistosity.

Shrinkage Stoping: A stoping method which uses part of the broken ore as a working platform and as support for the walls of the stope.

Siderite: Iron carbonate, which when pure, contains 48.2% iron; must be roasted to drive off carbon dioxide before it can be used in a blast furnace. (Roasted product is called sinter.)

Skarn: Name for the metamorphic rocks surrounding an igneous intrusive where it comes in contact with a limestone or dolomite formation.

Sphalerite: A zinc sulphide mineral; the most common ore mineral of zinc.

Step-out Drilling: Holes drilled to intersect a mineralized horizon or structure along strike or down dip.

Stockpile: Broken ore heaped on the surface, pending treatment or shipment.

Stope: An underground excavation from which ore has been extracted either above or below mine level.

Stratigraphy: Strictly, the description of bedded rock sequences; used loosely, the sequence of bedded rocks in a particular area.

Strike: The direction, or bearing from true north, of a vein or rock formation measured on a horizontal surface.

Stringer: A narrow vein or irregular filament of a mineral or minerals traversing a rock mass.

Stripping Ratio: The ratio of tons removed as waste relative to the number of tons of ore removed from an open pit mine.

Sublevel: A level or working horizon in a mine between main working levels.

Sulphide: A compound of sulfur and some other element.

Tailings: Material rejected from a mill after more of the recoverable valuable minerals have been extracted.

Tailings Pond: A low-lying depression used to confine tailings, the prime function of which is to allow enough time for heavy metals to settle out or for cyanide to be destroyed before water is discharged into the local watershed.

Trend: The direction, in the horizontal plane, or a linear geological feature (for example, an ore zone), measured from true north.

Troy Ounce: Unit of weight measurement used for all precious metals. The familiar 16-ounce avoirdupois pound equals 14.583 Troy Ounces.

Vein: A mineralized zone having a more or less regular development in length, width and depth which clearly separates it from neighboring rock.

Volcanogenic: A term used to describe the volcanic origin of mineralization.

Vug: A small cavity in a rock, frequently lined with well-formed crystals. Amethyst and quartz commonly forms in these cavities.

Wall Rocks: Rock units on either side of an orebody. The hanging-wall and footwall rocks of an orebody.

Waste: Barren rock in a mine, or mineralized material that is too low in grade to be mined and milled at a profit.

Winze: An internal shaft.

Zone of Oxidation: The portion of an orebody that has been oxidized, usually in the upper portion of the ore zone.


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