mineral

Potassium Feldspar

Orthoclase (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: typically pink, flesh-toned, or white; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: two planes at nearly 90 degrees; Specific gravity: 2.55–2.63

Hardness: 6 on Mohs scale
Color: typically pink, flesh-toned, or white
Luster: vitreous to pearly

Identified May 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily in igneous rocks like granite and pegmatites through the cooling of silica-rich magma; also found in metamorphic rocks and as a detrital component in sedimentary rocks like arkose.

Uses & applications

Extensively used in the manufacture of glass and ceramics (porcelain); also used as a filler in paints and plastics, and occasionally as a gemstone (moonstone variety).

Geological facts

Feldspars are the most abundant mineral group in the Earth's crust, making up about 60% of the terrestrial crust. The pink color in many granites is due to the presence of orthoclase.

Field identification & locations

Identify in the field by its distinct pinkish-to-tan color, its hardness (will scratch glass), and its characteristic right-angle cleavage planes. It is globally common in continental crust.