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.
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