(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.

plural of feldspar

(mineralogy) Any of several alkaline feldspars containing potassium aluminium silicate, KAlSi₃O₈

(obsolete, mineralogy) potassium feldspar

(mineralogy) sanidine

plural of potassium feldspar

plural of glassy feldspar

Resembling or characteristic of feldspar.