feldspar definition | Dictionary.com

feld⋅spar

[feld-spahr, fel-]

–noun

any of a group of minerals, principally aluminosilicates of potassium, sodium, and calcium, characterized by two cleavages at nearly right angles: one of the most important constituents of igneous rocks.

Also, felspar.

Origin:
1750–60; feld- (< G: field) + spar ³ ; r. feldspath < G (Feld field + Spath spar)

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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feld·spar (fěld'spär', fěl'-)

n. Any of a group of abundant rock-forming minerals occurring principally in igneous, plutonic, and some metamorphic rocks, and consisting of silicates of aluminum with potassium, sodium, calcium, and, rarely, barium. About 60 percent of the earth's outer crust is composed of feldspar.

[Partial translation of obsolete German Feldspath : Feld, field (from Middle High German veld, from Old High German feld; see pelə-² in Indo-European roots) + Spath, spar.]

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Feldspar

Feld"spar`\, Feldspath \Feld"spath`\, n. [G. feldspath; feld field + spath spar.] (Min.) A name given to a group of minerals, closely related in crystalline form, and all silicates of alumina with either potash, soda, lime, or, in one case, baryta. They occur in crystals and crystalline masses, vitreous in luster, and breaking rather easily in two directions at right angles to each other, or nearly so. The colors are usually white or nearly white, flesh-red, bluish, or greenish.

Note: The group includes the monoclinic (orthoclastic) species orthoclase or common potash feldspar, and the rare hyalophane or baryta feldspar; also the triclinic species (called in general plagioclase) microcline, like orthoclase a potash feldspar; anorthite or lime feldspar; albite or soda feldspar; also intermediate between the last two species, labradorite, andesine, oligoclase, containing both lime and soda in varying amounts. The feldspars are essential constituents of nearly all crystalline rocks, as granite, gneiss, mica, slate, most kinds of basalt and trachyte, etc. The decomposition of feldspar has yielded a large part of the clay of the soil, also the mineral kaolin, an essential material in the making of fine pottery. Common feldspar is itself largely used for the same purpose.

Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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feldspar

1757, from Ger. Feldspath, from Feld "field" + spath "spar, non-metallic mineral, gypsum."

feldspar (fěld'spär', fěl'-) Pronunciation Key
Any of a group of abundant monoclinic or triclinic minerals having the general formula MAl(Al,Si)₃O₈, where M is either potassium (K), sodium (Na), or calcium (Ca) or less commonly barium (Ba), rubidium (Rb), strontium (Sr), or iron (Fe). Feldspars range from white, pink, or brown to grayish blue in color. They occur in igneous, sedimentary, and metamorphic rocks and make up more than 60 percent of the Earth's crust. When they decompose, feldspars form clay or the mineral kaolinite.

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