A Adit An opening driven horizontally into the side of a mountain or hill for providing access to a mineral deposit. Assay A chemical test performed on a sample of ores or minerals to determine the amount of valuable metals contained. B 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. Broken reserves The ore in a mine which has been broken by blasting but which has not yet been transported to surface. C 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. Chute An opening usually constructed of timber and equipped with a gate, through which ore is drawn from a stope into mine cars. Clarification Process of clearing dirty water by removing suspended material. 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. 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. Core The long cylindrical piece of rock, about an inch in diameter, brought to the surface by diamond drilling. 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. D Decline A sloping underground opening for machine access from level to level or from surface; also called a ramp. Diamond drill A rotary type of rock drill that cuts a core of rock that is recovered in long cylindrical sections, two centimetres or more in diameter. Dip The angle at which a vein, structure or rock bed is inclined from the horizontal as measured at right angles to the strike. 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. G Greenstone belt An area underlain by metamorphosed volcanic and sedimentary rocks, usually in a continental shield.