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.
Many types of crushed stone: Crushed stone is not a "standardized commodity." It is made by mining one of several types of rock such as limestone, granite, trap rock, scoria, basalt, dolomite, or sandstone; crushing the rock; and then screening the crushed rock to sizes that are suitable for the intended end use.
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