Description
The mineral orthoclase is a potassium-aluminum tectosilicate with the chemical formula KAlSi3O8. It belongs to the feldspars. The transparent to translucent, colorless, white, pinkish-yellow orthoclase has a white streak color, a vitreous luster, and perfect cleavage along the [001] crystal plane and good cleavage along [010]. Its average density is 2.56 and its hardness is 6, by definition. The crystal system is monoclinic, and the radioactivity of orthoclase is barely measurable. Its gamma ray value, according to the American Petroleum Institute, is 200.97. The name of the mineral orthoclase is derived from the Greek words orthos ("straight") and klasos, meaning "to break." Orthoclase, the potassic end member of the (albite-orthoclase) potassium feldspar series, is a very common feldspar in both intrusive and extrusive igneous rocks and in metamorphic rocks.
