ardennite (ar-den'-nite). A yellow to yellowish-brown orthorhombic mineral: Mn2+4(Al,Mg)6(SiO4)2(Si3O10)[(As,V)O4](OH)6 .
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.
mottled zone . A layered that is marked with spots or blotches of different color or shades of color. The pattern of mottling and the size, abundance, and color contrast of the mottles may vary considerably and should be specified in the soil description. See also: soil color.
polarity interval . The fundamental unit of worldwide polarity-chronostratigraphic classification. The term is applied to rock, not time; it is used in a spatial sense (Oriel et al., 1976, p.276).
traverse table . A mathematical table listing the lengths of the two sides opposite the oblique angles for each of a series of right-angled plane triangles as functions of every degree of angle (azimuth or bearing) and of all lengths of the hypotenuse from 1 to 100. Traverse tables are used in computing latitudes and departures in surveying and courses in navigation.
dun . An inconspicuous hill in the English Lake District. Etymol: Gaelic.
gupeiite (gu-pei'-ite). A metallic steel-gray cubic mineral: Fe3Si .
Wheelerian (Wheel-er'-i-an). Western North America stage: upper Pliocene and Pleistocene (above Venturian).
plane of mirror symmetry . A symmetry element that is a plane dividing an object (crystal, array of atoms, etc.) into halves, one of which is the mirror image of the other. Syn: mirror plane of symmetry; plane of symmetry [cryst]; symmetry plane; reflection plane.
adapertural (ad-ap-er'-tur-al). Toward the aperture of a gastropod or cephalopod shell. Ant: abapertural. Syn: adoral.
majorite (ma'-jor-ite). A purple to pale yellowish-brown cubic meteorite mineral of the garnet group: Mg3(Fe,Al,Si)2(SiO4)3 . It possesses silicon in both tetrahedral and octahedral coordinations by oxygen.
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