Mining Terms

A

Adit

A horizontal passage from the surface into a mine. Sometimes called a tunnel.

Anomaly

A geological feature, esp. in the subsurface, distinguished by geological, geophysical, or geochemical means, which is different from the general surroundings and is often of potential economic value, and usually suggests the possibility of a mineral deposit.

Argillic

Pertaining to clay or clay minerals; e.g. "argillic alteration" in which certain minerals of a rock are converted to minerals of the clay group.

Arsenopyrite

A tin-white or silver-white to steel-gray mineral. Arsenopyrite occurs chiefly in crystalline rocks and esp. in lead and silver veins, and is constitutes the principal ore of arsenic.

Assay

To analyze the proportions of metals in an ore, to test an ore or mineral for composition, purity, weight, or other properties of commercial interest.

B

Backfilling

The process of refilling an excavation, a mine opening, or the space around a foundation.

Ball Mill

A rotating horizontal cylinder with a diameter almost equal to the length supported by a frame or shaft, in which nonmetallic materials are ground using various types of grinding media such as quartz pebbles, porcelain balls, etc.

Base Metal

(a) Any of the more common and more chemically active metals, e.g. lead, copper.

(b) The principal metal of an alloy, e.g. the copper in brass.

Bed / Beds

Perhaps the most common term in geology, meaning layer or stratum. Quarrymen usually mean by beds not the stone beds in the geologist's sense but the partings between them.

Bench

1. In an underground mine, a long horizontal face or ledge of ore in a stope or working place.

2. The horizontal step or floor along which coal, ore, stone, or overburden is worked or quarried.

Blade

A flattened, elongate mineral crystal.

Blasthole

A hole drilled in a material to be blasted, for the purpose of containing an explosive charge.

Breccias / Brecciating

A course-grained clastic rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix. The fragments have sharp edges and unworn corners.

By-product

A secondary metal or mineral product recovered in the milling process.

C

Calcareous

Said of a substance that contains calcium carbonate. When applied to a rock name it implies that as much as 50% of the rock is calcium carbonate.

Carbonaceous

(a) Said of a rock or sediment that is rich in carbon; coaly.

(b) Said of a sediment containing organic matter.

Carbonate

1. A mineral compound characterized by a fundamental anionic structure.

2. A sediment formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron; e.g. limestone and dolomite.

Carbon-in-leach

A recovery process in which a slurry of gold ore, carbon granules and cyanide are mixed together. The cyanide dissolves the gold content and the gold is adsorbed on the carbon: the carbon is subsequently separated from the slurry for further gold removal.

Carbon-in-pulp

A precious metals leaching technique in which granular activated carbon particles much larger than the ground ore particles are added to the cyanidation pulp after the precious metals have been solubilized. The activated carbon and pulp are agitated together to enable the solubilized precious metals to become adsorbed onto the activated carbon. The loaded activated carbon is mechanically screened to separate it from the barren ore pulp and processed to remove the precious metals and prepare it for reuse. Similar to carbon-in-leach process.

Chalcopyrite

A bright brass-yellow tetragonal mineral. It is generally found massive and constitutes the most important ore of copper.

Chert

A hard, extremely dense or compact, dull to semivitreous, sedimentary rock, consisting dominantly of interlocking crystals of quartz; it may contain amorphous silica (opal). It may be white or variously colored gray, green, blue, pink, red, yellow, brown, and black.

Collar

The mouth or upper end of a mine shaft.

Compression

A system of forces or stresses that tends to decrease the volume or to shorten a substance, or the change of volume produced by such a system of forces.

Contained Ounces

Represents ounces in the ground without the reduction of ounces not recovered by the applicable metallurgical process.

Concentrates

The valuable fraction of an ore that is left after worthless material is removed in processing.

Concentrator

1. A plant where ore is separated into values (concentrates) and rejects (tails). An appliance in such a plant, e.g., flotation cell, jig, electromagnet, shaking table. Also called mill; reduction works; cleaning plant.

2. An apparatus in which, by the aid of water, air, and/or gravity, mechanical concentration of ores is performed.

Core Hole

Any hole drilled for the purpose of obtaining cores; loosely, a well, generally shallow, drilled for geological information only.

Cut-and-fill

A stoping method in which the ore is excavated by successive flat or inclined slices, working upward from the level. However, after each slice is blasted down, all broken ore is removed, and the stope is filled with waste (backfill) up to within a few feet of the back before the next slice is taken out, just enough room being left between the top of the waste pile and the back of the stope to provide working space. The term cut-and-fill stoping implies a definite and characteristic sequence of operations: (1) breaking a slice of ore from the back;

(2) removing the broken ore; and

(3) introducing filling.

Cyanidation

A process of extracting gold and silver as cyanide slimes from their ores by treatment with dilute solutions of potassium cyanide or sodium cyanide. The slimes are subsequently fused and cast into ingots or bullion.

D

Dacite

A fine-grained extrusive rock.

Development

The preparation of a mining property or area so that an orebody can be analyzed and its tonnage and quality estimates have been made; ore essentially ready for mining.

Diamond Drilling

A variety of rotary drilling in which diamond bits are used as the rock-cutting tool. It is a common method of prospecting for mineral deposits, esp. in development work where core samples are desired.

Dike

A tabular igneous intrusion that cuts across the bedding or foliation of the country rock.

Dike Swarm

A group of dikes, which may be in radial, parallel, or en echelon arrangement. Their relationship with the parent plutonic body may not be directly observable.

Dilution

The contamination of ore with barren wall rock in stoping. The assay of the ore after mining is frequently 10% lower than when sampled in place.

Disseminated Ore

Said of a mineral deposit (esp. of metals) in which the desired minerals occur as scattered particles in the rock, but in sufficient quantity to make the deposit an ore.

Dore

Gold and silver bullion that remains in a cupelling furnace after the lead has been oxidized and skimmed off.

Drift

A horizontal or nearly horizontal underground opening driven along a vein to gain access to the deposit.

Dolomite

1. A common rock-forming mineral. Dolomite is white, colorless, or tinged yellow, brown, pink, or gray. Dolomite is found in extensive beds as dolomite rock; it is a common vein mineral.

2. A carbonate sedimentary rock consisting of dolomite, or a variety of limestone or marble rich in magnesium carbonate. Dolomite occurs in crystalline and noncrystalline forms, is clearly associated and often interbedded with limestone, and usually represents a postdepositional replacement of limestone.

E

Electrum

A naturally occurring, deep-yellow to pale-yellow alloy of gold with silver; argentiferous gold, containing more than 20% silver.

Erosion / Erosional

The group of physical and chemical processes by which earth or rock material is loosened or dissolved and removed from any part of the Earth's surface. It includes the processes of weathering, solution, corrosion, and transportation.

Extraction

(a) The process of mining and removal of coal or ore from a mine.

(b) The process of dissolving and separating out specific constituents of a sample by treatment with solvents specific for those constituents.

F

Fault Gouge

Soft, uncemented pulverized clay or claylike material, commonly a mixture of minerals in finely divided form, found along some faults or between the walls of a fault, and filling or partly filling a fault zone; a slippery mud that coats the fault surface or cements the fault breccia. It is formed by the crushing and grinding of rock material as the fault developed, as well as by subsequent decomposition and alteration caused by underground circulating solutions.

Fault Zone

A fault that is expressed as a zone of numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as hundreds of meters.

Fill

Man-made deposits of natural earth materials (e.g. rock, soil, gravel) and waste materials (e.g. tailings or spoil from dredging), used to fill an enclosed space such as an old stope or chamber in a mine.

Flotation

A process by which some mineral particles are induced to become attached to bubbles and float, and other particles to sink, so that the valuable minerals are concentrated and separated from the worthless gangue.

Foot Wall

The wall or the rock on the underside of a vein or ore deposit.

G

Galena

A bluish-gray to lead-gray mineral. It frequently contains included silver minerals. It has a shiny metallic luster, exhibits highly perfect cubic cleavage, and is relatively soft and very heavy. Galena is the most important ore of lead and one of the most important sources of silver.

Glacial Deposits

A general term for debris transported by glaciers or icebergs, and deposited directly on land or in the sea.

Glaciation

1. The formation, movement, and recession of glaciers or ice sheets.

2. The covering of large land areas by glaciers or ice sheets.

3. The geographic distribution of glaciers and ice sheets.

4. A collective term for the geologic processes of glacial activity, including erosion and deposition, and the resulting effects of such action on the Earth's surface.

5. Any of several minor parts of geologic time during which glaciers were more extensive than at present.

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 lowest grade of mineralized material that qualifies as ore in a given deposit; ore of the lowest assay value that is included in an ore estimate.

Mill Head Grade

The grade of ore as it comes from a mine and goes to a mill.

Recovered Grade

Actual metal content of ore determined after processing.

Reserve

The quantity of mineral that is calculated to lie within given boundaries. It is described as total (or gross), workable, or probable working, depending on the application of certain arbitrary limits in respect of deposit thickness, depth, quality, geological conditions, and contemporary economic factors. Proved, probable, and possible reserves are other terms used in general mining practice.

Gravity Circuit

A method by which mineral particles are separated with the aid of water or air, according to the differences in their specific gravities.

Grinding

Size reduction of ore into fine particles to prepare it for processing; comminution.

H

Hanging Wall

The overlying side of an orebody, fault, or mine working, esp. the wall rock above an inclined vein or fault.

Heap / Dump Leaching

A process used for the recovery of copper, uranium, and precious metals from weathered low-grade ore. The crushed material is laid on a slightly sloping, impervious pad and uniformly leached by the percolation of the leach liquor trickling through the beds by gravity to ponds. The metals are recovered by conventional methods from the solution.

Heap Leach Pad

A large impermeable foundation or pad used as a base for ore during heap leaching.

Hoist

The machine used for raising and lowering the cage or other conveyance in a shaft.

Host Rock

The rock surrounding an ore deposit.

Hydrothermal

Of or pertaining to hot water, to the action of hot water, or to the products of this action, such as a mineral deposit precipitated from a hot aqueous solution, with or without demonstrable association with igneous processes; also, said of the solution itself.

I

Impervious

Said of a rock that does not permit the passage of fluids under the pressure conditions ordinarily found in the subsurface.

Infill Drilling

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

Intercept

That portion included between two points in a borehole, as between the point where the hole first encounters a specific rock or mineral body and where the hole enters a different or underlying rock formation.

L

Leaching

The separation, selective removal, or dissolving-out of soluble constituents from a rock or orebody by the natural action of percolating water, or the extraction of soluble metals or salts from an ore by means of slowly percolating solutions.

Lode

A mineral deposit consisting of a zone of veins, veinlets, disseminations, or planar breccias; a mineral deposit in consolidated rock as opposed to a placer deposit.

Long-Hole Open Stope

A method of mining involving the drilling of holes up to 90 feet long into an ore body and then blasting a slice of rock which falls into an open space. The broken rock is extracted and the resulting open chamber is not filled with supporting material.

M

Metallurgy

The science and art of separating metals and metallic minerals from their ores by mechanical and chemical processes; the preparation of more metalliferous materials from raw ore.

Merrill Crowe Circuit or Merrill Crowe Process

Removal of gold from pregnant cyanide solution by deoxygenation, followed by precipitation on zinc dust, followed by filtration to recover the resultant auriferous gold slimes.

Milling Circuit

The combination of various processes and systems which concentrate the valuable minerals.

Mine

An excavation beneath the surface of the ground from which mineral matter of value is extracted.

Mineralization

The process or processes by which mineral or minerals are introduced into a rock, resulting in a valuable or potentially valuable deposit.

Mining Claim

That portion of public mineral lands which a party has staked or marked out in accordance with federal, provincial or state mining laws to acquire the right to explore for and exploit the minerals under the surface.

Mudstone

1. An indurated mud having the texture and composition of shale, but lacking its fine lamination or fissility; a blocky or massive, fine-grained sedimentary rock in which the proportions of clay and silt are approximately equal; a nonfissile mud shale. See also siltstone.

2. A general term that includes clay, silt, claystone, siltstone, shael, and argillite, and that should be used only when the amounts of clay and silt are not known or specified or cannot be precisely identified.

3. A term used for a mud-supported carbonate sedimentary rock containing less than 10% grains (particles with diameters greater than 20 microns); e.g. a calcilutite. The term specifies neither mineralogic composition nor mud of clastic origin.

O

Ore

Rock, generally containing metallic or non-metallic minerals, that can be mined and processed at a profit. Also, the mineral(s) thus extracted.

Orebody

A sufficiently large amount of ore that can be mined economically.

Ore Shoot

An elongated pipelike, ribbonlike, or chimneylike mass of ore within a deposit (usually a vein), representing the more valuable part of the deposit.

Ore Slurry

The fine carbonaceous discharge from a mine washery. All washeries produce some slurry, which must be treated to separate the solids from the water in order to have a clear effluent for reuse or discharge.

Overburden

Barren rock material, either loose or consolidated, overlying a mineral deposit, which must be removed prior to mining.

Oxide Ore

Mineralized rock in which some of the original minerals have been oxidized. Oxidation tends to make the ore more porous and permits a more complete permeation of cyanide solutions so that minute particles of gold in the interior of the minerals will be readily dissolved.

Oxidized Zone

An area of mineral deposits modified by surface waters, e.g. sulfides altered to oxides and carbonates.

P

Patenting

A process established under the General Mining Law of 1872 which permits the conversion of mining claims on federal lands into full fee ownership, provided certain conditions are met.

Permeable

Pertaining to a rock or soil having a texture that permits passage of liquids or gases under the pressure ordinarily found in earth materials.

Pregnant Pond

Pond containing solution which has percolated through the ore on a heap leach. The solution is impregnated with gold and silver removed from the ore.

Pyrite

A common, pale-bronze or brass-yellow, isometric mineral. It is dimorphous with marcasite, and often contains small amounts of other metals. Pyrite has a brilliant metallic luster and an absence of cleavage, and has been mistaken for gold. Pyrite is the most wide-spread and abundant of the sulfide minerals and occurs in all kinds of rocks, such as in nodules in sedimentary rocks and coal seams or as a common vein material associated with many different minerals.

Pyritization

Introduction of , or replacement by, pyrite; e.g. the replacement of the original material of the hard parts of certain fossil animals and plants by pyrite. Pyritization is a common process of hydrothermal alteration and often involves the introduction of fine-grained pyrite disseminated as specks in rock adjacent to veins.

Q

Quartz

1. Crystalline silica, an important rock-forming mineral. It is, next to feldspar, the commonest mineral, occurring either in transparent hexagonal crystals (colorless, or colored by impurities) or in crystalline or cryptocrystalline masses. Quartz is the commonest gangue mineral of ore deposits, forms the major proportion of most sands, and has a widespread distribution in igneous, metamorphic, and sedimentary rocks.

2. A general term for a variety of noncrystalline or cryptocrystalline minerals having the same chemical composition as that of quartz, such as chalcedony, agate, and opal.

Quartzite

1. A granoblastic metamorphic rock consisting mainly of quartz and formed by recrystallization of sandstone or chert by either regional or thermal metamorphism.

2. A very hard but unmetamorphosed sandstone, consisting chiefly of quartz grains that have been so completely and solidly cemented with secondary silica that the rock braks across or though the grains rather than around them. The cement grows in optical and crystallographic continuity around each quartz grain, thereby tightly interlocking the grains as the original pore spaces are filled.

R

Raise

A vertical hole between mine levels used to move ore or waste rock or to provide ventilation.

Ramp

An inclined underground tunnel which provides access for exploration or a connection between levels of a mine.

Reclamation

The process by which lands disturbed as a result of mining activity are reclaimed back to a beneficial land use. Reclamation activity includes the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas.

Recovery Rate

A term used in process metallurgy to indicate the proportion of valuable material obtained in the processing of an ore. It is generally stated as a percentage of the material recovered compared to the total material present.

Refining

The final stage of metal production in which impurities are removed from the molten metal.

Refractory Material

Gold mineralized material in which the gold is not amenable to recover by conventional cyanide methods without any pretreatment. The refractory nature can be either silica or sulphide encapsulation of the gold or the presence of naturally occurring carbons which reduce gold recovery. Material of this nature is difficult or expensive to recover its valuable constituents.

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. There are two categories of reserves:

Proven Ore

Material for which tonnage and grade are computed from dimensions revealed in outcrops, trenches, underground workings or drill holes; grade is computed from the results of adequate sampling; and the sites for inspection, sampling and measurement are so spaced and the geological character so well-defined that size, shape and mineral content are established.

Probable Ore

Material for which tonnage and grade are computed partly from specific measurements, samples or production data and partly from projection for a reasonable distance on geological evidence: and for which the sites available for inspection, measurement and sampling are too widely or otherwise inappropriately spaced to outline the material completely or to establish its grade throughout.

Resource

A Mineral Resource is 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.

Measured Mineral Resource

A Measured Mineral Resource is 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.

Indicated Mineral Resource

An Indication Mineral Resource is 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, ppits, workings and drill holes that are spaced closely enough for geological and grade continuity to be reasonably assumed.

Inferred Mineral Resource

An Inferred Mineral Resource is 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.

Reverse Circulation Drilling

Drilling that produces rock chips rather than core. Faster and cheaper than diamond drilling, the chips are forced by air to surface for examination.

Reverse Circulation Holes

Holes drilled using a process where the circulation of bit-coolant and cuttings-removal liquids, drilling fluid, mud, air, or gas down the borehole outside the drill rods and upward inside the drill rods. Also called countercurrent; counterflush.

Rhyolite

A group of extrusive, igneous rocks.

S

Sediment

Solid fragmental material that originates from weathering of rocks and is transported or deposited by air, water, or ice, or that accumulates by other natural agents, such as chemical precipitation from solution or secretion by organisms, and that forms in layers on the Earth's surface at ordinary temperatures in a loose, unconsolidated form; e.g., sand, gravel, silt, mud, alluvium.

Semi-autogenous Grinding (SAG)

A method of grinding rock into fine powder whereby the grinding media consist of larger chunks of rocks and steel balls.

Sericitic

Pertaining to a hydrothermal, deuteric or metamorphic process involving the introduction of, alteration to, or replacement by sericitic muscovite.

Shaft

A vertical passageway to an underground mine for moving personnel, equipment, supplies and material including ore and waste rock.

Sheeted Veins

A group of closely spaced, distinct parallel fractures filled with mineral matter and separated by layers of barren rock.

Shotcrete

A mixture made of course aggregate up to 2 cm thick, applied by pneumatic pressure through a specially adapted hose and used as a fireproofing agent and as a sealing agent to prevent weathering of mine timbers and roadways.

Sill

1. A tabular igneous intrusion that parallels the planar structure of the surrounding rock.

2a. A submarine ridge or rise at a relatively shallow depth, separating a basin from another basin or from an adjacent sea and causing the basin to be partly closed, e.g. in the Straits of Gibraltar.

2b. A ridge of bedrock or earth material at a shallow depth near the mouth of a fjord, separating the deep water of the fjord from the deep ocean water outside.

Slurry

A mixture of crushed and finely ground solids with water.

Smelting

A metallurgical operation in which metal is separated from impurities by a process that includes fusion.

Spot Bolting

The use of one or just a few roof bolts at spot locations.

Stockwork

A mineral deposit consisting of a three-dimensional network of planar to irregular veinlets closely enough spaced that the whole mass can be mined.

Stope

An area in an underground mine where ore is mined.

Stratum / Strata

A bed or layer of rock; strata, more than one layer.

Strike Fault

A fault whose strike is parallel to the strike of the strata.

Strike Length

The longest horizontal dimension of an ore body or zone of mineralization.

Stripping Ratio

The ratio of the number of tons of waste material removed to the number of tons of ore removed, used in connection with open pit mining.

Sulphide Ore

A sub-group of refractory ore - mineralized rock in which much of the gold is encapsulated in sulphides and is not readily amenable to dissolution by cyanide solutions - associated with sulphide minerals (primarily pyrite) that have not been oxidized. Some sulphide ore may require autoclaving or roasting prior to cyanidation.

T

Tailings

The material that remains after all metals considered economic have been removed from ore during milling.

Tailings Dam

A natural or man-made area suitable for depositing the material that remains after the treatment of ore.

Thickener

A vessel or apparatus for reducing the proportion of water in a pulp by means of sedimentation.