feldspar

Noun. (mineralogy) 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.

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This entry was last updated on RefTopia from its source on 3/20/2012.