petrography (pe-trog'-ra-phy). That branch of geology dealing with the description and systematic classification of rocks, esp. igneous and metamorphic rocks and esp. by means of microscopic examination of thin sections. Petrography is more restricted in scope than petrology. Adj: petrographic. See also: lithology; sedimentary petrography.
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.
sartorite (sar'-to-rite). A gray monoclinic mineral: PbAs2S4 . Syn: scleroclase.
curvatura (cur-va-tu'-ra). A visible line of some mid-Paleozoic trilete spores that connects the extremities of the ends of the laesura and outlines the contact areas; e.g. a "curvatura perfecta" having three lines complete all around the spore's proximal face, or a "curvatura imperfecta" having forklike projections from the radial ends of the laesura but not joining with their neighbors. Pl: curvaturae.
statute mile (stat'-ute). A measure of distance used on land, equal to 5,280 ft, 1,760 yd, 1,609.35 m, 1.61 km, 880 fathoms, 80 chains, 320 rods, or 8,000 links, and roughly equivalent to 0.87 international nautical miles. It is usually referred to as mile.
spatial sediment concentration . The sediment contained in a unit volume of flow used to measure transport concentration.
apochete (ap'-o-chete). An exhalant canal of a sponge.
rhizocretion (rhi-zo-cre'-tion). A term used by Kindle (1923, p.631) for a hollow concretionlike mass that had formed around the root of a living plant. Cf: rhizoconcretion.
wolgidite (wol'-gid-ite). A lamproite that contains leucite, magnophorite, diopside, and minor amounts of olivine and phlogopite. The name, given by Wade and Prider in 1940, is from the Wolgidee Hills, Western Australia. Mitchell and Bergman (1991) suggest that this name should be replaced by diopside-leucite-richterite madupitic lamproite . Obsolete.
sinhalite (sin'-ha-lite). A hard colorless, yellow, pink, greenish, or brown orthorhombic mineral: MgAlBO4 . It is structurally related to monticellite .
seismic source . (a) A device for generating seismic waves. (b) The point at which seismic waves are generated. (c) The point of origin of an earthquake.
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