a white to pale yellow, red, or green mineral of the feldspar group, found in igneous, sedimentary, and metamorphic rocks. It is used in the manufacture of glass and ceramics. Composition: potassium aluminium silicate. Formula: KAlSi3O8. Crystal structure: monoclinic
(ôr'thə-klās') A white, pink, yellow, or brown type of potassium feldspar. It is dimorphous with microcline, being more stable at higher temperatures than it is. Also called: potash feldspar. Chemical formula: KAlSi3O8.