The classification of stoping methods adopted by the U.S. Bureau of Mines, devised largely on the basis of rock stability, is as follows: (1) stopes naturally supported--this includes open stoping with open stopes in small orebodies, and sublevel stoping; and open stopes with pillar supports that includes casual pillars and room (or stope) and 3120 pillar (regular arrangement); (2) stopes artifically supported--this includes shrinkage stoping, with pillars, without pillars, and with subsequent waste filling; cut-and-fill stoping; stulled stopes in narrow veins; and square-set stoping; (3) cave stopes--this includes caving (ore broken by induced caving), block caving, including caving to main levels and caving to chutes or branched raises; sublevel caving and top slicing (mining under a mat that, together with caved capping, follows the mining downward in successive stages); and (4) combinations of supported and caved stopes (as shrinkage stoping with pillar caving, cut-and-fill stoping with top slicing of pillars, etc.)