37 roof bolting A method of supporting the ceilings of underground mines by inserting long steel bolts into holes bored into the strata forming the roof rotary drill A drill machine that rotates a rigid tu bular string of rods to which is attached a bit for cutting rock to produce boreholes scrubber Any of several forms of chemicalphysi cal devices that remove sulfur compounds formed during coal combustion Technically known as fue gas desulfurization systems they combine the sul fur in gaseous emissions with another chemical medium to form an inert sludge shaft A narrow deep excavation used for fnding or mining ore or coal The term is often applied to vertical shafts as distinguished from a decline or inclined shaft shortwall A deep mining method in which small areas are worked by a continuous miner in con junction with longwalllike hydraulic roof supports Accounts for less than one percent of total under ground coal production shuttle car A selfdischarging truck usually with rubber tires or caterpillartype treads used for receiving coal or ore from the loading or mining machine and transferring it to an underground crusher loading point mine railway or belt con veyor system slurry pipeline A pipeline similar to that used by the petroleum and natural gas industries designed for transporting pulverized coal in a liquid medium Water is usually used although research is focusing on other compounds such as oil liquid methane and carbon dioxide slope mine A mine with an opening that slopes upward or downward to the seam It must also have adjoining vertical shafts for air ventilation and emergency use smelter A furnace in which the raw materials are melted and metals are separated from impurities steam coal Coal used by electric power plants and industrial steam boilers to produce electricity stope An excavation from which ore has been removed in a series of steps strategic minerals Those minerals considered essential for a countrys economic and defense needs such as metals for defense weapons satellite communications automobile parts and medical instruments subbituminous coal See ranks of coal surface mine A mine in which the coal lies near the surface and can be extracted by removing the covering layer of overburden About 66 percent of total US coal production comes from surface mines tailings The waste material left after hardrock mining and milling processes have been complet ed tipple A surface processing structure for cleaning and sizing coal and automatically loading it onto rail cars or trucks for movement to market tunnel A horizontal underground passage that opens to the surface at both ends turbine A machine in which rotating vanes are driven by a steam generator to produce electricity underground mine Also known as a deep mine Usually located several hundred feet below the earths surface an underground mines coal is re moved mechanically and transferred by shuttle car or conveyor to the surface Most underground mines are located east of the Mississippi River and account for about 34 percent of total annual US coal production unit train A long train of between 60 and 150 or more hopper cars carrying only coal between a single mine and destination A typical unit train can carry at least 10000 tons of coal in a single shipment G L O SSA R Y