Back:  The ceiling or roof of an underground opening.
Backfill:  Waste material used to fill the void created by mining an ore body.
Background:  Minor amounts of radioactivity, shown on a counter, that are due to cosmic rays and minor residual radioactivity in the vicinity and not to abnormal amounts of radioactive minerals nearby.
Backwash:  Water movement against the primary direction of flow.
Back sample:  Rock chips collected from the roof or back of an underground opening for the purpose of determining grade.
Bacterial leaching / bio-oxidation:  The use of bacteria to oxidize sulfide minerals.
Baffle:  A partition or grating in a furnace, container or channel.
Bailer:  Device for removing sludge and water from a drill hole or mine.
Bajadas:  Spanish for desert alluvial fans.
Ball mill:  A cylindrically shaped steel container filled with steel balls into which crushed ore is fed. The ball mill is rotated, causing the balls to cascade, which in turn grinds the ore into small particles in preparation for concentration.
Banded iron formation:  Rock composed of bands or layers of minerals (rocks) differing in color and texture.
Bank Cubic Meter:  A cubic meter of rock in place before it is drilled and blasted; a volumetric term commonly used in coal mining in place of the weight measure (tonnes) used in metal mining.
Basalt:  An extrusive volcanic rock composed primarily of plagioclase, pyroxene and minor 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:  Center of operations from which exploration activity is conducted.
Base metal:  Any non-precious metal (e.g. copper, lead, zinc, nickel, etc.).
Base:  Any compound that will combine with an acid and neutralize it, forming a salt; also bottom or support for any structure.


Underlying fundamental; rocks with little silica; also the opposite of acidic.
Basic rocks:  An igneous rock, relatively low in silica and composed mostly of dark-colored minerals.
Batea:  Early type wooden gold pan.
Batholith:  A large mass of igneous rock extending to great depth with its upper portion dome-like in shape. It has crystallized below surface, but may be exposed as a result of erosion of the overlying rock. Smaller masses of igneous rocks are known as bosses or plugs.


A rock made up of hydrous aluminum oxides; the most common aluminum ore layers.
Beach placer:  A placer deposit of valuable heavy minerals on a contemporary or ancient beach or along a coastline.
Bedded:  Refers to rock formations deposited in successive layers.
Bedded Lead:  A term used to describe planar quartz veins confined by the bedding planes of metamorphosed sedimentary rocks. Commonly used to describe gold-bearing quartz veins in Nova Scotia.
Bedding:  The arrangement of sedimentary rocks in layers.


Solid rock forming the Earth's crust, frequently covered by soil or water.
Bench:  Exposed cut in ancient river bed.
Benches:  Natural or man-made step-like terraces.
Beneficiate:  To concentrate or enrich; often applied to the preparation of iron ore for smelting, through such processes as sintering, magnetic concentration, washing, etc.
Bentonite:  An aluminum silicate clay which has great ability to absorb water and which swells accordingly. It is formed from volcanic ash and used in various adhesives, cements, and ceramic fillers.
Bessemer:  An iron ore which has a very low phosphorus content.
Beta particles:  An elementary particle emitted from the nucleus of an element during radioactive decay.
Bio-leaching:  A process for recovering metals from low-grade ores by dissolving them in solution, the dissolution being aided by bacterial action.
Biosphere:  That part of the Earth which contains living things.
Biotite:  A platy magnesium-iron mica, common in igneous rocks.
Bit:  The cutting end of a drill frequently made of an ultra-hard material such as industrial diamonds or tungsten carbide.
Black gold:  Placer gold that is coated with black manganese oxides.
Black Jack:  A miner's term for sphalerite or zinc blend.
Black sands:  A mixture of heavy, dark minerals and metals.
Black smoker:  Tall volcanic vent found along active spreading centers on the ocean floor through which laden-laden fluids escape.
Blackballed:  A term that is given to a miner who was caught stealing and all other mining operations in the area know and thus refuse to hire the miner.


A mine employee responsible for loading, priming and detonating blastholes.
Blasting:  Detonating explosives to loosen rock for excavation.
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. Iron ore is most commonly treated in this way, and so are some ores of copper, lead, etc.
Blasthole:  A hole drilled for purposes of blasting rather than for exploration or geological information.
Blister copper:  The product of the Bessemer converter furnace used in copper smelting. It is a crude form of copper, assaying about 99% copper, and 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.
Boiling Point:  The point at which a substance boils; for water, 212 degrees F. or 100 degrees C.
Bonanza:  Very rich ore.
Boom:  A telescoping, hydraulically powered steel arm on which drifters, manbaskets and hydraulic hammers are mounted.
Borehole:  Common term for a drill hole.
Borer:  Common term for rock-cutting drill.
Bort:  An impure diamond used for hardening drill bits; an abrasive.
Botryoidal:  Refers to mineral occurring in globular forms.
Boulder clay:  An unstratified deposit of clay in which are embedded rock particles up to the size of boulders; usually of glacial origin.
Box hole:  A short raise or opening driven above a drift for the purpose of drawing ore from a stope, or to permit access.
Brace:  Mine timber; also platform over mouth of vertical shaft.
Break:  A loose term used to describe a large scale regional shear zone or structural fault.
Breaker:  Slang term for a rock crusher.
Breast:  A working face, usually restricted to a stope.
Breccia:  A type of rock whose components are angular in shape, as distinguished from a conglomerate, whose components are water- worn into a rounded shape.
Brittle:  Easily fractured or broken.
Broken reserves:  The amount of 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, useful for sighting lines, measuring dip and carrying out preliminary surveys.
Bucket line dredge:  A large dredge that utilizes a chain of buckets to excavate and lift gravels for processing.
Bulkhead:  Partition erected to seal off certain portions of mines.
Bulk mining:  Any large-scale, mechanized method of mining involving many thousands of tonnes of ore being brought to surface per day by a relatively few number of miners.

Bulk sample: 

A large sample of mineralization, frequently involving hundreds of tonnes, selected in such a manner as to be representative of the potential orebody being sampled. Used to determine metallurgical characteristics.


Moving material with mechanized equipment.
Bullion:  Metal in bars, ingots or other uncoined form.
Bull quartz:  A prospector's term describing white, coarse-grained, barren quartz.
Butte:  An isolated hill or mountain with steep sides.
Button:  Refers to precious metal globule produced by fire assaying.
Byproduct:  A secondary metal or mineral product recovered in the milling process.