Definitions for orthoclaseˈɔr θəˌkleɪs, -ˌkleɪz
Random House Webster's College Dictionary
or•tho•claseˈɔr θəˌkleɪs, -ˌkleɪz(n.)
a common white or pink potassium feldspar mineral, KAlSi3O8, having two good cleavages at right angles, and found in silica-rich igneous rocks.
Origin of orthoclase:
a white or colored monoclinic feldspar
Potassium aluminum silicate, KAlSiO, a common feldspar of igneous, plutonic, and metamorphic rocks. Orthoclase is the main feldspar of pegmatite occurrences, where it is most commonly flesh-colored. Orthoclase is used in the ceramic and glass industries and as a decorative gravel.