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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bobtraillite . A vitreous gray, pale green, or brown hexagonal mineral: Na15Sr12Zr14Si42B6O138(OH)6•12H2O.

Butterworth filter . A frequency filter characterized by a very flat passband, often used as an alias filter. Sometimes called a maximally flat filter or trapezoidal filter (Sheriff and Geldart, 1995).

macroclimate (mac-ro-cli'-mate). The general climate of an extensive region or a country. See also: mesoclimate; microclimate.

fumarole mound . A small mound from which fumarole or solfatara gases escape.

alumino-katophorite . A hypothetical member of the amphibole mineral family; probably an unnecessary name for katophorite : Na2Ca(Fe2+4Al)(Si7Al)O22(OH)2.

clarotelain (clar-o-te'-lain). A transitional lithotype of coal characterized by the presence of telinite, with lesser amounts of other macerals. Cf: teloclarain. Syn: clarotelite.

oboyerite (o-boy'-er-ite). A white triclinic mineral: H6(Pb,Ca)6(Te4+O3)3(Te6+O6)2•2H2O .

greenstone [meta] . A field term applied to any compact dark-green altered or metamorphosed mafic igneous rock (e.g., spilite, basalt, gabbro, diabase) that owes its color to the presence of chlorite, actinolite, or epidote.

sanderite (san'-der-ite). An incompletely described mineral: MgSO4•2H2O.

anticyclone (an-ti-cy'-clone). An atmospheric high-pressure system with closed isobars, the pressure gradient being directed away from the center so that the near surface wind spirals outward in a clockwise direction in the Northern Hemisphere, counterclockwise in the Southern. It was named by Francis Galton in 1861. See also: cyclone.


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