Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminum silicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks.

from the GNU version of the Collaborative International Dictionary of English

  • n. 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.

from The Century Dictionary and Cyclopedia

  • n. In mineralogy, one of a very common group of closely related minerals, all silicates of aluminium, together with either calcium, sodium, potassium, or in one case barium.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. any of a group of hard crystalline minerals that consist of aluminum silicates of potassium or sodium or calcium or barium

Etymologies

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.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Feld, field (from Middle High German veld, from Old High German feld) + Spath, spar (Wiktionary)

Examples

  • The name feldspar is a contraction of the longer name fieldspar, as some early specimens were found in fields.

    Feldspar

  • Sand, the proppant, primarily quartz and feldspar aka ground up rock, is the material that gets lodged in cracks that open up, and keep those cracks open when force and pressure are removed, allowing less resistance between underground hydrocarbons, to allow them to become newly liberated hydrocarbons, which we use to power a significant portion of our country.

    Energy 101: Hydraulic Fracturing - Vladimir’s blog - RedState

  • (Common orthoclase feldspar, which is frequently of a brownish pink or flesh color, will do.)

    A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public

  • In other cases, quartz is the predominant material, and in still other cases, where the best kaolin is produced, the proportion of both quartz and mica are small, and the feldspar is the prevailing material.

    North Carolina and its Resources.

  • Simple inspection will show that granite rock, for example, is a mixture of three minerals, called feldspar, mica, and quartz.

    Religion and Chemistry

  • The rock here is a porphyritic granite (porhyritic meaning that the stone has large-grained crystals, such as feldspar or quartz, dispersed in a fine-grained feldspathic matrix or groundmass).

    Of Books and the Sea

  • In the process of weathering, the softer, weaker minerals in granite (such as feldspar) are weathered away.

    Sand and gravel

  • Melters such as feldspar, whiting (or limestone) and talc are sufficient for the higher temperatures above 1200

    2. Kilns

  • There is also added some more fusible substance, such as feldspar, gypsum, or lime, together with some pure quartz.

    An Elementary Study of Chemistry

  • Basalt includes smaller amounts of light colored minerals such as feldspar and quartz.

    Yahoo! Answers: Latest Questions

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  • Feldspar, the Jewish rock!

    June 5, 2007

  • There's nothing funny about feldspar, folks.

    December 13, 2006