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[feld-spahr, fel-] /ˈfɛldˌspɑr, ˈfɛl-/
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 of feldspar
1750-60; feld- (< German: field) + spar3; replacing feldspath < German (Feld field + Spath spar) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for feldspar
  • Until now, scientists had believed the moon was made of two basic types of rock: dark basalt and light, calcium-rich feldspar.
  • Andesite is a gray, fine-grained volcanic rock, chiefly composed of plagioclase feldspar.
  • The coarse feldspar grains enclosed within the enclave are the same as the feldspar grains that make up the granite outside it.
  • In various proportions are feldspar and traces of other minerals.
  • feldspar in the rock is moderately to intensely altered to sericite and clay minerals.
  • feldspar phenocrysts typically are labradorite to andesine in composition.
British Dictionary definitions for feldspar


/ˈfɛldˌspɑː; ˈfɛlˌspɑː/
any of a group of hard rock-forming minerals consisting of aluminium silicates of potassium, sodium, calcium, or barium: the principal constituents of igneous rocks. The group includes orthoclase, microcline, and the plagioclase minerals
Derived Forms
feldspathic (fɛldˈspæθɪk; fɛlˈspæθ-), felspathic, feldspathose, felspathose, adjective
Word Origin
C18: from German feldspat(h), from feld field + spat(h) spar³
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for feldspar

1785, earlier feldspath (1757), from German Feldspath (Modern German Feldspat), from Feld "field" (see field (n.)) + spath "spar, non-metallic mineral, gypsum" (see spar (n.2)); spelling influenced by English spar "mineral."

Online Etymology Dictionary, © 2010 Douglas Harper
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feldspar in Science
  (fěld'spär', fěl'-)   
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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