[feld-spahr, fel-]


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)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for feldspar

Historical Examples of feldspar

  • I do hope I 'll get one with feldspar in it, or something nice and interesting.

    The Wrong Woman

    Charles D. Stewart

  • Granite is made of quartz, mica, and feldspar, as has been said before.

    Diggers in the Earth

    Eva March Tappan

  • Feldspar as an abrasive is used mainly in scouring soaps and window-wash.

  • When flint and feldspar are used, they are ground fine at the quarry.

    Makers of Many Things

    Eva March Tappan

  • According to the color of the feldspar the rock may be red, or pink, or gray.

    The Elements of Geology

    William Harmon Norton

British Dictionary definitions for feldspar




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 Formsfeldspathic (fɛldˈspæθɪk, fɛlˈspæθ-), felspathic, feldspathose or felspathose, adjective

Word Origin for feldspar

C18: from German feldspat (h), from feld field + spat (h) spar ³
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

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

feldspar in Science


[fĕldspär′, fĕl-]

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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.