Acidic precipitation – Snow and rain that have a low pH, caused by sulphur dioxide and nitric oxide gases from industrial activity released into the atmosphere.
Acidic rocks – Igneous rock carrying a high (greater than 65%) proportion of silica.
Acid mine drainage – Acidic run-off water from mine waste dumps and mill tailings ponds containing sulphide minerals. Also refers to ground water pumped to surface from mines.
Adit – An opening driven horizontally into the side of a mountain or hill for providing access to a mineral deposit.
Aerial magnetometer – An instrument used to measure magnetic field strength from an airplane.
Aeromagnetic survey – A geophysical survey using a magnetometer aboard, or towed behind, an aircraft.
Agglomerate – A breccia composed largely or entirely of fragments of volcanic rocks.
Agglomeration – A method of concentrating valuable minerals based on their adhesion properties.
Agitation – In metallurgy, the act or state of being stirred or shaken mechanically, sometimes accomplished by the introduction of compressed air.
Airborne survey – A survey made from an aircraft to obtain photographs, or measure magnetic properties, radioactivity, etc.
Alloy – A compound of two or more metals.
Alluvium – Relatively recent deposits of sedimentary material laid down in river beds, flood plains, lakes, or at the base of mountain slopes. (adj. alluvial)
Alpha meter – An instrument used to measure positively charged particles emitted by radioactive materials.
Alpha ray – A positively charged particle emitted by certain radioactive materials.
Alteration – Any physical or chemical change in a rock or mineral subsequent to its formation. Milder and more localized than metamorphism.
Amorphous – A term applied to rocks or minerals that possess no definite crystal structure or form, such as amorphous carbon.
Amortization – The gradual and systematic writing off of a balance in an account over an appropriate period.
Amphibolite – A gneiss or schist largely made up of amphibole and plagioclase minerals.
ANFO – Acronym for ammonium nitrate and fuel oil, a mixture used as a blasting agent in many mines.
Annual report – The formal financial statements and report on operations issued by a corporation to its shareholders after its fiscal year-end.
Anode – A rectangular plate of metal cast in a shape suitable for refining by the electrolytic process.
Anomaly – Any departure from the norm which may indicate the presence of mineralization in the underlying bedrock.
Anthracite – A hard, black coal containing a high percentage of fixed carbon and a low percentage of volatile matter.
Anticline – An arch or fold in layers of rock shaped like the crest of a wave.
Apex – The top or terminal edge of a vein on surface or its nearest point to the surface.
Ash – The inorganic residue remaining after ignition of coal.
Assay – A chemical test performed on a sample of ores or minerals to determine the amount of valuable metals contained.
Assay foot (metre, inch, centimetre) – The assay value multiplied by the number of feet, metres, inches, centimetres across which the sample is taken.
Assay map – Plan view of an area indicating assay values and locations of all samples taken on the property.
Assessment work – The amount of work, specified by mining law, that must be performed each year in order to retain legal control of mining claims.
Authorized capital – see capital stock.
Autogenous grinding – The process of grinding ore in a rotating cylinder using large pieces of the ore instead of conventional steel balls or rods.
Back – The ceiling or roof of an underground opening.
Backfill – Waste material used to fill the void created by mining an orebody.
Background – Minor amounts of radioactivity due not to abnormal amounts of radioactive minerals nearby, but to cosmic rays and minor residual radioactivity in the vicinity.
Back sample – Rock chips collected from the roof or back of an underground opening for the purpose of determining grade.
Backwardation – A situation when the cash or spot price of a metal stands at a premium over the price of the metal for delivery at a forward date.
Balance sheet – A formal statement of the financial position of a company on a particular day, normally presented to shareholders once a year.
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.
Banded iron formation – A bedded deposit of iron minerals.
Basalt – An extrusive volcanic rock composed primarily of plagioclase, pyroxene and some olivine.
Basal till – Unsorted glacial debris at the base of the soil column where it comes into contact with the bedrock below.
Basement rocks – The underlying or older rock mass. Often refers to rocks of Precambrian age which may be covered by younger rocks.
Base camp – Centre of operations from which exploration activity is conducted.
Base metal – Any non-precious metal (eg. copper, lead, zinc, nickel, etc.).
Basic rocks – Igneous rocks that are relatively low in silica and composed mostly of dark-colored minerals.
Batholith – A large mass of igneous rock extending to great depth with its upper portion dome-like in shape. Similar, smaller masses of igneous rocks are known as bosses or plugs.
Bauxite – A rock made up of hydrous aluminum oxides; the most common aluminum ore.
Bear market – Term used to describe market conditions when share prices are declining.
Bedding – The arrangement of sedimentary rocks in layers.
Beneficiate – To concentrate or enrich; often applied to the preparation of iron ore for smelting.
Bentonite – A clay with great ability to absorb water and which swells accordingly.
Bessemer – An iron ore with a very low phosphorus content.
Bio-leaching – A process for recovering metals from low-grade ores by dissolving them in solution, the dissolution being aided by bacterial action.
Biotite – A platy magnesium-iron mica, common in igneous rocks.
Bit – The cutting end of a drill frequently made of an extremely hard material such as industrial diamonds or tungsten carbide.
Blackjack – A miner’s term for sphalerite (zinc sulphide).
Black smoker – Volcanic vent found in areas of active ocean floor spreading, through which sulphide-laden fluids escape.
Blaster – A mine employee responsible for loading, priming and detonating blastholes.
Blast furnace – A reaction vessel in which mixed charges of oxide ores, fluxes and fuels are blown with a continuous blast of hot air and oxygen-enriched air for the chemical reduction of metals to their metallic state.
Blasthole – A drill hole in a mine that is filled with explosives in order to blast loose a quantity of rock.
Blister copper – A crude form of copper (assaying about 99%) produced in a smelter, which requires further refining before being used for industrial purposes.
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.
Board lot – One hundred shares.
Bond – An agreement to pay a certain amount of interest over a given period of time.
Boom – A telescoping, hydraulically powered steel arm on which drifters, manbaskets and hydraulic hammers are mounted.
Box hole – A short raise or opening driven above a drift for the purpose of drawing ore from a stope, or to permit access.
Break – Loosely used to describe a large-scale regional shear zone or structural fault.
Breast – A working face in a mine, usually restricted to a stope.
Breccia – A rock in which angular fragments are surrounded by a mass of fine-grained minerals.
Broken reserves – The ore in a mine which has been broken by blasting but which has not yet been transported to surface.
Brunton compass – A pocket compass equipped with sights and a reflector, used for sighting lines, measuring dip and carrying out preliminary surveys.
Bulk mining – Any large-scale, mechanized method of mining involving many thousands of tonnes of ore being brought to surface per day.
Bulk sample – A large sample of mineralized rock, frequently hundreds of tonnes, selected in such a manner as to be representative of the potential orebody being sampled. Used to determine metallurgical characteristics.
Bullion – Metal formed into bars or ingots.
Bull market – Term used to describe financial market conditions when share prices are going up.
Bull quartz – A prospector’s term for white, coarse-grained, barren quartz.
Byproduct – A secondary metal or mineral product recovered in the milling process.
Cable bolt – A steel cable, capable of withstanding tens of tonnes, cemented into a drillhole to lend support in blocky ground.
Cage – The conveyance used to transport men and equipment between the surface and the mine levels.
Calcine – Name given to concentrate that is ready for smelting (i.e. the sulphur has been driven off by oxidation).
Call – An option to buy shares at a specified price. The opposite of a “put”.
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.
Captive stope – A stope that is accessible only through a manway.
Carbon-in-pulp – A method of recovering gold and silver from pregnant cyanide solutions by adsorbing the precious metals to granules of activated carbon, which are typically ground up coconut shells.
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.
Cathode – A rectangular plate of metal, produced by electrolytic refining, which is melted into commercial shapes such as wirebars, billets, ingots, etc.
Cesium magnetometer – An geophysical instrument which measures magnetic field strength in terms of vertical gradient and total field.
Chalcocite – A sulphide mineral of copper common in the zone of secondary enrichment.
Chalcopyrite – A sulphide mineral of copper and iron; the most important ore mineral of copper.
Change house – The mine building where workers change into work clothes; also known as the “dry”.
Channel sample – A sample composed of pieces of vein or mineral deposit that have been cut out of a small trench or channel, usually about 10 cm wide and 2 cm deep.
Charter – A document issued by a governing authority creating a company or other corporation.
Chartered bank – A financial institution that accepts deposits and provides loans.
Chip sample – A method of sampling a rock exposure whereby a regular series of small chips of rock is broken off along a line across the face.
Chromite – The chief ore mineral of chromium.
Chute – An opening, usually constructed of timber and equipped with a gate, through which ore is drawn from a stope into mine cars.
Cinnabar – A vermilion-colored ore mineral of mercury.
Circulating load – Over-sized chunks of ore returned to the head of a closed grinding circuit before going on to the next stage of treatment.
Claim – A portion of land held either by a prospector or a mining company. In Canada, the common size is 1,320 ft. (about 400 m) square, or 40 acres (about 16 ha).
Clarification – Process of clearing dirty water by removing suspended material.
Classifier – A mineral-processing machine which separates minerals according to size and density.
Clay – A fine-grained material composed of hydrous aluminum silicates.
Cleavage – The tendency of a mineral to split along crystallographic planes.
Closed circuit – A loop in the milling process wherein a selected portion of the product of a machine is returned to the head of the machine for finishing to required specification.
Coal – A carbonaceous rock mined for use as a fuel.
Coalification – The metamorphic processes of forming coal.
Collar – The term applied to the timbering or concrete around the mouth of a shaft; also used to describe the top of a mill hole.
Column flotation – A milling process, carried out in a tall cylindrical column, whereby valuable minerals are separated from gangue minerals based on their wetability properties.
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 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.
Concentrator – A milling plant that produces a concentrate of the valuable minerals or metals. Further treatment is required to recover the pure metal.
Confirmation – A form delivered by a broker to the client, setting forth the details of stock sales or purchases for the client.
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.
Contact metamorphism – Metamorphism of country rocks adjacent to an intrusion, caused by heat from the intrusion.
Contango – A situation in which the price of a metal for forward or future delivery stands at a premium over the cash or spot price of the metal.
Continuous miner – A piece of mining equipment which produces a continuous flow of ore from the working face.
Controlled blasting – Blasting patterns and sequences designed to achieve a particular objective. Cast blasting, where the muck pile is cast in a particular direction, and deck blasting, where holes are loaded once but blasted in successive blasts days apart, are examples.
Converter – In copper smelting, a furnace used to separate copper metal from matte.
Core – The long cylindrical piece of rock, about an inch in diameter, brought to surface by diamond drilling.
Core barrel – That part of a string of tools in a diamond drill hole in which the core specimen is collected.
Cordillera – The continuous chain of mountain ranges on the western margin of North and South America.
Country rock – Loosely used to describe the general mass of rock adjacent to an orebody. Also known as the host rock.
Crosscut – A horizontal opening driven from a shaft and (or near) right angles to the strike of a vein or other orebody.
Crust – The outermost layer of the Earth; includes both continental and oceanic crust.
Cum-dividend – Buyer entitled to pending dividend payment.
Current assets – Assets of company which can and are likely to be converted into cash within a year. Includes cash, marketable securities, accounts receivable and supplies.
Current liabilities – A company’s debts that are payable within a year’s time.
Custom smelter – A smelter which processes concentrates from independent mines. Concentrates may be purchased or the smelter may be contracted to do the processing for the independent company.
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 value – Applies to assays that have been reduced to some arbitrary maximum to prevent erratic high values from inflating the average.
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.
Cyanide – A chemical species containing carbon and nitrogen used to dissolve gold and silver from ore.
Day order – An order to buy or sell shares, good only on the day the order was entered.
Debenture – See bonds.
Debt financing – Method of raising capital whereby companies borrow money from a lending institution.
Deck – The area around the shaft collar where men and materials enter the cage to be lowered underground.
Decline – A sloping underground opening for machine access from level to level or from surface; also called a ramp.
Deferred charges – Expenses incurred but not charged against the current year’s operation.
Depletion – An accounting device, used primarily in tax computations. It recognizes the consumption of an ore deposit, a mine’s principal asset.
Depreciation – The periodic, systematic charging to expense of plant assets reflecting the decline in economic potential of the assets.
Development – Underground work carried out for the purpose of opening up a mineral deposit. Includes shaft sinking, crosscutting, drifting and raising.
Development drilling – drilling to establish accurate estimates of mineral reserves.
Diabase – A common basic igneous rock usually occurring in dykes or sills.
Diamond – The hardest known mineral, composed of pure carbon; low-quality diamonds are used to make bits for diamond drilling in rock.
Diamond drill – A rotary type of rock drill that cuts a core of rock that is recovered in long cylindrical sections, two cm or more in diameter.
Diamond driller – A person who operates a diamond drill.
Dilution (mining) – Rock that is , by necessity, removed along with the ore in the mining process, subsequently lowering the grade of the ore.
Dilution (of shares) – A decrease in the value of a company’s shares caused by the issue of treasury shares.
Diorite – An intrusive igneous rock composed chiefly of sodic plagioclase, hornblende, biotite or pyroxene.
Dip – The angle at which a vein, structure or rock bed is inclined from the horizontal as measured at right angles to the strike.
Dip needle – A compass with the needle mounted so as to swing in a vertical plane, used for prospecting to determine the magnetic attraction of rocks.
Directional drilling – A method of drilling involving the use of stabilizers and wedges to direct the orientation of the hole.
Discount – The minimum price below the par value at which treasury shares may legally be sold.
Disseminated ore – Ore carrying small particles of valuable minerals spread more or less uniformly through the host rock.
Dividend – Cash or stock awarded to preferred and common shareholders at the discretion of the company’s board of directors.
Dividend claim – Made when a dividend has been paid to the previous holder because stock has not yet been transferred to the name of the new owner.
Dor bar – The final saleable product of a gold mine. Usually consisting of gold and silver.
Drag fold – The result of the plastic deformation of a rock unit where it has been folded or bent back on itself.
Drawpoint – An underground opening at the bottom of a stope through which broken ore from the stope is extracted.
Drift – A horizontal underground opening that follows along the length of a vein or rock formation as opposed to a crosscut which crosses the rock formation.
Drifter – A hydraulic rock drill used to drill small-diameter holes for blasting or for installing rock bolts.
Drill-indicated reserves – The size and quality of a potential orebody as suggested by widely spaced drillholes; more work is required before reserves can be classified as probable or proven.
Dry – A building where the miner changes into working clothes.
Due diligence – The degree of care and caution required before making a decision; loosely, a financial and technical investigation to determine whether an investment is sound.
Dump – A pile of broken rock or ore on surface.
Dyke – A long and relatively thin body of igneous rock that, while in the molten state, intruded a fissure in older rocks.
Electrolysis – An electric current is passed through a solution containing dissolved metals, causing the metals to be deposited onto a cathode.
Electrolytic refining – The process of purifying metal ingots that are suspended as anodes in an electrolytic bath, alternated with refined sheets of the same metal which act as starters or cathodes.
EM survey – A geophysical survey method which measures the electromagnetic properties of rocks.
En echelon – Roughly parallel but staggered structures.
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.
Epigenetic – Orebodies formed by hydrothermal fluids and gases that were introduced into the host rocks from elsewhere, filling cavities in the host rock.
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.
Equity financing – The provision of funds by buying shares.
Era – A large division of geologic time – the Precambrian era, for example.
Erosion – The breaking down and subsequent removal of either rock or surface material by wind, rain, wave action, freezing and thawing and other processes.
Erratic – Either a piece of visible gold or a large glacial boulder.
Escrowed shares – Shares deposited in trust pending fulfilment of certain conditions, and not ordinarily available to trading until released.
Ex-dividend – On stocks selling “ex-dividend”, the seller retains the right to a pending dividend payment.
Exploration – Prospecting, sampling, mapping, diamond drilling and other work involved in searching for ore.
Face – The end of a drift, crosscut or stope in which work is taking place.
Fault – A break in the Earth’s crust caused by tectonic forces which have moved the rock on one side with respect to the other.
Feldspar – A group of common rock-forming minerals that includes microcline, orthoclase, plagioclase and others.
Felsic – Term used to describe light-colored rocks containing feldspar, feldspathoids and silica.
Ferrous – Containing iron.
Fine gold – Fineness is the proportion of pure gold or silver in jewelry or bullion expressed in parts per thousand. Thus, 925 fine gold indicates 925 parts out of 1,000, or 92.5% is pure gold.
Fissure – An extensive crack, break or fracture in rocks.
Fixed Assets – Possessions such as buildings, machinery and land which, as opposed to current assets, are unlikely to be converted into cash during the normal business cycle.
Float – Pieces of rock that have been broken off and moved from their original location by natural forces such as frost or glacial action.
Flotation – A milling process in which valuable mineral particles are induced to become attached to bubbles and float as others sink.
Flowsheet – An illustration showing the sequence of operations, step by step, by which ore is treated in a milling, concentration or smelting process.
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 chemical substance that reacts with gangue minerals to form slags, which are liquid at furnace temperature and low enough in density to float on the molten bath of metal or matte.
Fluxgate magnetometer – An instrument used in geophysics to measure total magnetic field.
Fold – Any bending or wrinkling of rock strata.
Footwall – The rock on the underside of a vein or ore structure.
Forward contract – The sale or purchase of a commodity for delivery at a specified future date.
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 resorting to pressure leaching or other chemical treatment.
Gabbro – A dark, coarse-grained igneous rock.
Galena – Lead sulphide, the most common ore mineral of lead.
Gamma – A unit of measurement of magnetic intensity.
Gangue – The worthless minerals in an ore deposit.
Geiger counter – An instrument used to measure the radioactivity that emanates from certain minerals by means of a Geiger-Mueller tube.
Geochemistry – The study of the chemical properties of rocks.
Geology – The science concerned with the study of the rocks which compose the Earth.
Geophysics – The study of the physical properties of rocks and minerals.
Geophysical survey – A scientific method of prospecting that measures the physical properties of rock formations. Common properties investigated include magnetism, specific gravity, electrical conductivity and radioactivity.
Geothermal – Pertains to the heat of the Earth’s interior.
Glacial drift – Sedimentary material that has been transported by glaciers.
Glacial striations – Lines or scratches on a smooth rock surface caused by glacial abrasion.
Glory hole – An open pit from which ore is extracted, especially where broken ore is passed to underground workings before being hoisted.
Gneiss – A layered or banded crystalline metamorphic rock, the grains of which are aligned or elongated into a roughly parallel arrangement.
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.
Gossan – The rust-colored capping or staining of a mineral deposit, generally formed by the oxidation or alteration of iron sulphides.
Gouge – Fine, putty-like material composed of ground-up rock found along a fault.
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.
Graben – A downfaulted block of rock.
Granite – A coarse-grained intrusive igneous rock consisting of quartz, feldspar and mica.
Gravity meter, gravimeter – An instrument for measuring the gravitational attraction of the earth; gravitational attraction varies with the density of the rocks in the vicinity.
Greenstone belt – An area underlain by metamorphosed volcanic and sedimentary rocks, usually in a continental shield. Grizzly (or mantle) – 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.
Gross value – The theoretical value of ore determined simply by applying the assay of metal or metals and the current market price. It must be used only with caution and severe qualification.
Gross value royalty – A share of gross revenue from the sale of minerals from a mine.
Grouting – The process of sealing off a water flow in rocks by forcing a thin slurry of cement or other chemicals into the crevices; usually done through a diamond drill hole.
Grubstake – Finances or supplies of food, etc., furnished to a prospector in return for an interest in any discoveries made.
Guides – The timber rails installed along the walls of a shaft for steadying, or guiding, the cage or conveyance.
Gypsum – A sedimentary rock consisting of hydrated calcium sulphate.
Gyratory crusher – A machine that crushes ore between an eccentrically mounted crushing cone and a fixed crushing throat. Typically has a higher capacity than a jaw crusher.
Halite – Rock salt.
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 whereby valuable metals, usually gold and silver, are leached from a heap, or pad, of crushed ore by leaching solutions percolating down through the heap and collected from a sloping, impermeable liner below the pad.
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.
Hematite – An oxide of iron, and one of that metal’s most common ore minerals.
High grade – Rich ore. As a verb, it refers to selective mining of the best ore in a deposit.
High-grader – One who steals rich ore, especially gold, from a mine.
Hoist – The machine used for raising and lowering the cage or other conveyance in a shaft.
Holding company – A corporation engaged principally in holding a controlling interest in one or more other companies.
Hornfels – A fine-grained contact metamorphic rock.
Horse – A mass of waste rock lying within a vein or orebody.
Horst – An upfaulted block of rock.
Host rock – The rock surrounding an ore deposit.
Hydrometallurgy – The treatment of ore by wet processes, such as leaching, resulting in the solution of a metal and its subsequent recovery.
Hydrothermal – Relating to hot fluids circulating in the earth’s crust.
Igneous rocks – Rocks formed by the solidification of molten material from far below the earth’s surface.
Ilmenite – An ore mineral of titanium, being an iron-titanium oxide.
Induced polarization – A method of ground geophysical surveying employing an electrical current to determine indications of mineralization.
Industrial minerals – Non-metallic, non-fuel minerals used in the chemical and manufacturing industries. Examples are asbestos, gypsum, salt, graphite, mica, gravel, building stone and talc.
Initial public offering – The first sale of shares to the public, usually by subscription from a group of investment dealers.
Institutional investors – Pension funds and mutual funds, managing money for a large number of individual investors.
Intermediate rock – An igneous rock containing 52% to 66% quartz.
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.
Ion exchange – An exchange of ions in a crystal with irons in a solution. Used as a method for recovering valuable metals, such as uranium, from solution.
Jaw crusher – A machine in which rock is broken by the action of steel plates.
Jig – A piece of milling equipment used to concentrate ore on a screen submerged in water, either by the reciprocating motion of the screen or by the pulsation of water through it.
Kimberlite – A variety of peridotite; the most common host rock of diamonds.