Stoping. Extraction of ore in an underground mine by working laterally in a series of levels or steps in the plane of a vein. It is generally done from lower to upper levels, so that the whole vein is ultimately removed. The process is distinct from working in a shaft or tunnel or in a room in a horizontal drift, although the term is used in a general sense to mean the extraction of ore.

Stratiform. Having the form of a layer, bed, or stratum; consisting of roughly parallel bands or sheets.

Sulfate. A mineral compound characterized by the sulfate radical SO4. Anhydrous sulfates, such as barite, BaSO4, have divalent cations linked to the sulfate radical; hydrous and basic sulfates, such as gypsum, CaSO4·2H2O, contain water molecules.

Sulfide. A mineral compound characterized by the linkage of sulfur with a metal or semimetal, such as galena (PbS) or pyrite (FeS2).

Suspended load. The part of the total sediment load that is carried for a considerable period of time in suspension, free from contact with the bed; it consists mainly of clay, silt, and sand.

Tailings. The gangue and other refuse material resulting from the washing, concentration, or treatment of ground ore.

Tectonics. A branch of geology dealing with the broad architecture of the outer part of the Earth, that is, the regional assembling of structural or deformational features, a study of their mutual relations, origin, and historical evolution.

Tuberculosis. A usually chronic, highly variable disease that is caused by a bacterium of the genus Mycobacterium (M. tuberculosis), is usually communicated by inhalation of the airborne causative agent, affects especially the lungs but may spread to other areas from local lesions or by way of the lymph or blood vessels, and is characterized by fever, cough, difficulty in breathing, inflammatory infiltrations, formation of tubercles, caseation, pleural effusion, and fibrosis.

Unconformity. The structural relationship between rock strata in contact, characterized by a lack of continuity in deposition, and corresponding to a period of nondeposition, weathering, or especially erosion (either subaerial or subaqueous) prior to the deposition of the younger beds, and often (but not always) marked by absence of parallelism between the strata.

Vein. An epigenetic mineral filling of a fault or other fracture in a host rock, in tabular or sheetlike form, often with associated replacement of the host rock; a mineral deposit of this form and origin.

Water table. The surface between the zone of saturation and the zone of aeration; that surface of a body of unconfined groundwater at which the pressure is equal to that of the atmosphere.

Watershed. The region drained by, or contributing water to, a stream, lake, or other body of water.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement