mineral
Potassium feldspar
Orthoclase or microcline; KAlSi₃O₈
AI-generated identification · may be incorrectTypically salmon-pink to reddish-brown, with a vitreous to pearly luster and prominent cleavage in two directions near 90°. Mohs hardness 6, monoclinic (orthoclase) or triclinic (microcline), and specific gravity about 2.55–2.63; the image appears to show a massive, weathered feldspar specimen.
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Physical properties
Typically salmon-pink to reddish-brown, with a vitreous to pearly luster and prominent cleavage in two directions near 90°. Mohs hardness 6, monoclinic (orthoclase) or triclinic (microcline), and specific gravity about 2.55–2.63; the image appears to show a massive, weathered feldspar specimen.
Formation & geological history
Forms by crystallization from silica-rich igneous melts, especially granite and syenite, and occurs in metamorphic rocks and pegmatites. Potassium feldspar is abundant in Precambrian and younger continental crust.
Uses & applications
Used in ceramics, porcelain, glass, glazes, abrasives, and mineralogical specimens; attractive varieties may be cut as gemstones, including orthoclase and amazonite (green microcline).
Geological facts
Feldspar is the most abundant mineral group in Earth’s crust. Pink coloration commonly results from iron impurities, while perthitic intergrowths and cleavage are characteristic of potassium feldspar.
Field identification & locations
Identify it by pink or cream color, blocky cleavage, hardness near 6, and inability to scratch glass easily or be scratched by a steel knife. Common localities include granitic terrains and pegmatites worldwide, notably Madagascar, Russia, Brazil, India, and the United States.
