A. Abutment - In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front abutment, that is, the solid coal ahead of the face and the back abutment, that is, the settled packs behind the face.
Underground hard rock mining refers to various underground mining techniques used to excavate hard minerals, usually those containing metals such as ore containing gold, silver, iron, copper, zinc, nickel, tin and lead, but also involves using the same techniques for excavating ores of gems such as diamonds or rubies.
The CrazyCrusher brand Rock Crusher is 100 percent steel, and it is 100 percent made in the U.S.A. by 100 percent Americans! The jaws are made of 3/8 steel, and the face has horizontal welds across them that not only help grip and pull down rock pieces, it also prevents wear on the actual jaws.
Back — The roof or upper part in any underground mining cavity. Backfill — Mine waste or rock used to support the roof after coal removal. Barren — Said of rock or vein material containing no minerals of value, and of strata without coal, or containing coal in seams too thin to be workable.
Mining was Zimbabwe's leading industry in 2002, contributing 27% of export trade. The chief minerals were coal, gold, copper, nickel, tin, and clay, and Zimbabwe was a world leader in the production of lithium minerals, chrysotile asbestos, and ferrochromium, with more than half of the world's known chromium reserves.
A crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust.. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated.