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.
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.
What is Quartz? Quartz is a chemical compound consisting of one part silicon and two parts oxygen. It is silicon dioxide (SiO 2).It is the most abundant mineral found at Earth's surface, and its unique properties make it one of the most useful natural substances.
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.