[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. |
| feld·spar (fěld'spär', fěl'-) 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. [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.] |
