Mining

Mining, extraction of minerals and ores from the earth. There are various types of mines. The open pit mine is used when the desired minerals lie near the surface. It usually consists of a series of terraces that are worked back in parallel so that the mineral is always within reach of the excavating machines. In strip mining a surface layer is peeled off to reach a usually thin mineral seam (often coal). When minerals lie far below the surface, various deep mining techniques must be used. Access to the mineral-bearing strata is obtained through a vertical shaft or sloping incline dug from the surface or through a horizontal adit driven into the side of a mountain. Underground mines require ventilation and lighting, facilities for pumping out any ground-water or toxic gases, and some means (railroad or conveyor) for carrying the ore and waste to the surface. Several serious occupational diseases (e.g., pneumoconiosis, or “black lung”) are associated with mining and extractive metallurgy, particularly where high dust levels and toxic substances are involved.