desert rose . A radially symmetric group of crystals with a fancied resemblance to a rose, formed in sand, soft sandstone, or clay. The crystals are usually of calcite, less commonly of barite, gypsum, or celestite.
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.
monzonorite (mon-zo-nor'-ite). In Tobi's classification (1971, p.202) of the charnockite series, a quartz-poor member containing more plagioclase than microperthite.
lath-shaped . Said of the habit of a crystal that is long and thin, and of moderate to narrow width. In thin section, lath-shaped crystals are often cross sections of platy or tabular crystals.
level rod . A straight rod or bar, with a flat face graduated in plainly visible linear units with zero at the bottom, used in measuring the vertical distance between a point on the Earth's surface and the line of sight of a leveling instrument that has been adjusted to a horizontal position. It is usually made of metal or well-seasoned wood. See also: target rod; self-reading leveling rod. Syn: rod [surv]; leveling rod; surveyor's rod.
bedrock . A general term for the rock, usually solid, that underlies soil or other unconsolidated, superficial material. A British syn. of the adjectival form is solid, as in solid geology.
clinographic projection . An oblique projection used for representing crystals in such a manner that no crystal face will be projected as a line.
exotic marker . An easily recognized spore ( Lycopodium ) or pollen ( Eucalyptus globosus ), of which a fixed number is added during the preparation of a known amount of sample, so that the relative abundance of palynomorphs obtained from that sample can be determined.
jacquesdietrichite . A vitreous blue orthorhombic mineral: Cu2BO(OH)5.
agpaitic (ag-pa-it'-ic). (a) Said of crystallization in the presence of an excess of alkali (esp. sodium), so that the amount of aluminum oxide is insufficient for the formation of aluminum silicates (Thrush, 1968, p.18). (b) Said of rocks with an agpaitic coefficient > 1.
pholad (pho'-lad). Any bivalve mollusk belonging to the family Pholadidae, characterized by an equivalve shell of variable size, commonly gaping open at the posterior end.
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