roomandpillar mining. Longwall mines need continuous mining machines (similar to those used in roomandpillar mines) to block out panels of coal. Plus, longwall mines need the specialized longwall, with its rugged and very expensive shields, cutters, and conveyors. A large initial capital outlay is required, and there
Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef or placer deposits form a mineralized package that is of economic interest to the miner. Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay.