Applies to establishments engaged in underground mining, not covered by another classification (N.O.C.), involving the extraction of coal, ores, stone, clay or other minerals. Operations contemplated by this classification include excavation and tunneling below ground as well as the incidental activities occurring above ground. Underground mining may involve shaft sinking, slope sinking, rock tunneling, and the building of drifts and shafts with heavy timbers or steel beams. Material is broken loose within the tunnel or shaft with explosives, drilling machines, rock drills, chippers, power hand drills and picks. After the material is broken loose it is removed from underground by way of hoist, conveyor, or some type of haulage car on steel track. On the surface, some of the extracted material is further refined such as coal which is crushed, screened, washed and graded before being hauled away. Additional equipment includes elevators, ventilation and communication systems, water pipes, lighting systems, as well as front end loaders, bulldozers and trucks. This classification also applies to establishments engaged in the manufacture of coke which is a solid carbonaceous residue obtained from bituminous coal after the removal of volatile materials by a distillation process. The method usually consists of a beehive or by-product oven process. Coal is fed into crushers which breaks oversized pieces into smaller pieces which are then conveyed to bunkers serving the ovens. This classification also applies to ore reduction involving heat processes.

This classification excludes ore reduction operations which do not require the use of heat which are to be reported separately in classification 1701, and open cut mining which is to be reported separately in classification 1703.