/feld"spahr', fel"-/ , n.
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.
Also, felspar .
[ 1750-60; feld- ( 3 ; r. feldspath Feld field + Spath spar) ]