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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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.

equatorial limb . A term sometimes applied to the amb of a pollen grain or spore. It is undesirable because of possible confusion. Syn: limb [palyn].

ahlfeldite (ahl'-feld-ite). A brownish-pink monoclinic mineral: NiSe4+O3•2H2O . It is isostructural with clinochalcomenite and cobaltomenite.

lowmoor peat . Peat occurring on low-lying moors or swamps and containing little or no sphagnum. Its moisture is standing surface water and is low in acidity. Mineral matter and nitrogen content is high compared to highmoor peat; cellulose content is low. Cf: highmoor peat; planar peat; topogenous peat. Syn: fen peat.

conchiolin (con-chi-o'-lin). A fibrous protein, C3H48N9O11, that constitutes the organic basis of most mollusk shells; e.g. the material of which the periostracum and organic matrix of the calcareous parts of a mollusk shell are composed. Syn: conchyolin.

lintisite . A colorless to pale yellow monoclinic mineral: Na3LiTi2O2(SiO3)4•2H2O.

macrophagous (mac-roph'-a-gous). Said of an organism that feeds on relatively large particles. Cf: microphagous.

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