backs
The height of ore available above a given working level. If the orebody has been proved by shaft sinking to a depth of 300 ft (91 m) from the surface, the orebody is said to have 300 ft (91 m) of backs.

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.

benefication
The dressing or processing of ores for the purpose of (1) regulating the size of a desired product, (2) removing unwanted constituents, and (3) improving the quality, purity, or assay grade of a desired product.

chalcopyrite
A tetragonal mineral, CuFeS₂ ; brass-yellow with bluish tarnish; massive; softer than pyrite; occurs in late magmatic hydrothermal veins and secondary enrichment zones; the most important source of copper.

crosscut
A horizontal opening driven across the course of a vein or in general across the direction of the main workings. A connection from a shaft to a vein.

Dorr rake classifier
A mechanical classifier consisting of an inclined settling tank and a rake-type conveying agitating mechanism. Feed introduced at the low end of the tank flows over a distributing apron toward the high end of the tank. The heavier materials of sand size settle into the rake zone and are raked up the slope and out the tank; slime and finer sands are carried over the rear wall in suspension.

drift
A horizontal gallery driven from one underground working place to another and parallel to the strike of the ore.

enargite
An orthorhombic mineral, Cu₃AsS₄ ; dimorphous with luzonite, metallic gray-black; in vein and replacement copper deposits as small crystals or granular masses; an important ore of copper and arsenic; may contain up to 7% antimony.

flotation cell
Appliance in which froth flotation of ores is performed. It has provision for receiving conditioned pulp, aerating this pulp and for separate discharge of the resulting mineralized froth and impoverished tailings.

foot wall
The underlying side of a fault, orebody, or mine working; esp. the wall rock beneath an inclined vein or fault.

froth flotation
The separating of finely crushed minerals from one another by causing some to float in a froth and others to remain in suspension in the pulp.

Frue vanner
An ore-beneficiation apparatus consisting essentially of a rubber belt traveling up a slight inclination. The material to be treated is washed by a constant flow of water while the entire belt is shaken from side to side.

galena
An isometric mineral, 4[PbS] ; cubic cleavage; forms cubes and octahedra, also coarse- or fine-grained masses; specific gravity, 7.6; occurs with sphalerite in hydrothermal veins, also in sedimentary rocks as replacement deposits; an important source of lead and silver. Also spelled galenite.

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