feldspar

Alternative forms

• felspar

Etymology

A partial calque of German Feldspat, formed from Feld (“field”) + Spat (“spar”).

Noun

feldspar (countable and uncountable, plural feldspars)

1. (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.