GeoWord of the Day

The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.

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chrysocolla (chrys-o-col'-la). (a) A blue, blue-green, or emerald-green amorphous mineral: Cu2(OH)4[Si2O3(OH)2]. It occurs as incrustations and thin seams in the zone of weathering of copper ores. Its chemical composition was formerly given as: CuSiO3•2H2O. (b) An old name given to a mineral or minerals (such as chrysocolla, borax, and malachite) used for soldering gold (Hey, 1962, p.384).

cubic law . An empirical observation that the volumetric flux of water through a fracture bounded by smooth parallel walls is proportional to the cube of its aperture. Originally derived by Boussinesq in 1868.

niobokupletskite . A beige to brown triclinic mineral of the astrophyllite group: K2Na(Mn,Zn,Fe)7(Nb,Zr,Ti)2Si8O26(OH,O,F)5. It is the Nb analogue of kupletskite.

serpentine-hosted asbestos . A mineral-deposit type characterized by stockworks of chrysotile asbestos in serpentinized ultramafic rocks. Syn: ultramafic-hosted asbestos.

side . (a) A slope of a mountain, hill, or bank; e.g. hillside. (b) A bank, shore, or other land bordering a body of water; e.g. seaside. (c) A geographic region; e.g. "countryside".

deuterostome . Coelomate animals in which the embryonic blastopore becomes the anus.

duricrust (du'-ri-crust). A general term for a hard crust on the surface of, or layer in the upper horizons of, a soil in a semiarid climate. It is formed by the accumulation of soluble minerals deposited by mineral-bearing waters that move upward by capillary action and evaporate during the dry season. See also: ferricrete; silcrete; calcrete; caliche [soil]. Etymol: Latin "durus", "hard", + crust. Cf: hardpan.

double tide . (a) A high tide consisting of two high-water maxima of nearly the same height separated by a slight lowering of water. (b) A low tide consisting of two low-water minima separated by a slight rise of water.

biophile (bi'-o-phile). (a) Said of those elements that are the most typical in organisms and organic material (Rankama & Sahama, 1950, p.88). (b) Said of those elements that are concentrated in and by living plants and animals (Goldschmidt, 1954, p.26).

white earth . A siliceous earthy material that is used as a pigment in paint.

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