protogranular (pro-to-gran'-u-lar). Said of the xenomorphic, granoblastic texture of a rock, characterized by sinuous mineral boundaries, intergrowths, and other features suggesting previous equilibrium with a melt (Mercier and Nicolas, 1975).
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.
pin [surv] . A sharp pointed metal rod with a ring at the end, used for marking taped measurements on the ground. A chaining pin set has 11 pins with two carrying rings. After 10 tape lengths are measured, the forward chainperson has an empty ring and rear chainperson has a ring with 10 pins. The last pin in the ground marks the end of the "tally" (Brinker and Wolf, 1977, p.59).Syn: arrow.
ascension theory (as-cen'-sion). A theory of hypogene mineral-deposit formation in which mineralizing solutions rise through fissures from magmatic sources in the Earth's interior. Cf: descension theory.
hexagonal close packing (hex-ag'-o-nal). In a crystal, close packing of atoms by stacking close-packed layers in the sequence ABAB etc. Cf: cubic close packing. See also: close-packed structure .
matted structure . A microstructure of, in general, mutually isolated, predominantly horizontal, elongated crystallites oriented in more or less random directions in the plane of their lamina (Peyer, 1968; Carter, 1990). The "Glanzschicht" or "shiny layer" of Preuschoft et al. (1974) for the dense vitrodentine or enameloid covering of shark fangs and cutting teeth.
adamsite-(Y) . A colorless or white triclinic mineral: NaY(CO)•6H2O.
barometric leveling . A type of indirect leveling in which differences of elevation are determined from differences of atmospheric pressure observed with altimeters or barometers. Cf: thermometric leveling.
coherent diffracting domain . The volume of crystal that is without defects and yet sufficiently large to serve as a diffraction grating, producing a coherent X-ray beam (Klug and Alexander, 1974, chap.9). Sometimes called "coherent scattering domain." Abbrev: CDD.
ciliate (cil'-i-ate). n. Any protozoan belonging to the class Ciliata and characterized by the presence of cilia throughout its life cycle. Range, Upper Jurassic to Holocene. adj. Possessing cilia.
mosandrite (mo-san'-drite). A colorless, greenish, reddish-brown, or yellowish-brown monoclinic mineral: (Na,Ca)3(Ca,Ce)3(Ti,Nb,Al,Zr)(Si2O7)2(O,F)4. Cf: johnstrupite. Syn: rinkite; rinkolite; lovchorrite; khibinite [mineral].
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