RFG 2018 Conference

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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compensator . An apparatus in a polarizing microscope that measures the phase difference between two components of polarized light, e.g. a Berek compensator or a biquartz plate.

Unwin's critical velocity (Un'-win's). critical velocity (e).

motukoreaite (mo-tu'-ko-rea'-ite). A white to pale yellow-green rhombohedral mineral related to hydrotalcite: [Mg6Al3(OH)18][Na0.6(SO4,CO3)2]•12H2O .

stress drop . The decrease in differential stress that occurs in the vicinity of a fault following slip on the fault.

serir (se-rir'). A desert plain strewn with rounded pebbles, older than the gravel-covered reg; a stony desert from which the sand has been blown away, as in the Sahara of Libya and Egypt. Etymol: Arabic, "dry". Pl: serir. Cf: pebble armor; hammada.

strontio-orthojoaquinite . A yellow orthorhombic mineral: Na(Ba,Sr)4Fe3+Ti2Si8O24(OH)4. It is a dimorph of strontiojoaquinite.

patchy gas . Small accumulations of gas that present potential hazards but of no commercial value.

insoluble residue (in-sol'-u-ble). The material remaining after the more soluble part of a rock sample has been dissolved in, e.g., hydrochloric acid or acetic acid. It is chiefly composed of siliceous material (e.g. chert or quartz) and various detrital minerals (e.g. anhydrite, glauconite, pyrite, and sphalerite). Abbrev: IR. See also: siliceous residue.

convolution [sed struc] (con-vo-lu'-tion). (a) The process of producing convolute bedding; the state of being convoluted. (b) A structure produced by convolution, such as a small-scale but intricate fold. (c) convolute bedding.

crystal gliding . Deformation of crystalline material by orderly displacement of atoms such that good crystal structure remains after the process is finished. It often produces crystal twins. See also: twin gliding. Syn: gliding [cryst]; translation gliding.


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