mineral

Potassium Feldspar (Orthoclase / Microcline)

KAlSi3O8

Hardness: 6 on Mohs scale. Color: Salmon-pink to reddish-orange, tan. Luster: Vitreous to pearly. Crystal structure: Monoclinic or Triclinic. Cleavage: Perfect cleavage in two directions at near 90-degree angles. Specific gravity: 2.56-2.59.

Hardness: 6 on Mohs scale
Color: Salmon-pink to reddish-orange, tan
Luster: Vitreous to pearly

Identified July 24, 2026More mineral →

Explore Potassium Feldspar (Orthoclase / Microcline) in the encyclopedia →

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Physical properties

Formation & geological history

Forms primarily in igneous rocks such as granite and pegmatite through the cooling and crystallization of magma, as well as in metamorphic rocks like gneiss.

Uses & applications

Widely used in the manufacture of glass, ceramics, porcelain, and mild abrasives. High-grade polished pieces or varieties (like sunstone or moonstone) are used in jewelry and decorative stone work.

Geological facts

Potassium feldspar is one of the defining minerals on Mohs hardness scale, marking the benchmark for a hardness of 6. Feldspars as a group make up over 50% of Earth's crust.

Field identification & locations

Identified by its distinct salmon-pink or orange-red color, vitreous luster, and right-angle cleavage planes displaying flat step-like surfaces. Commonly found in granitic terrains, pegmatites, and gravels worldwide.

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Metamorphic

Sandstone with Mineral Veining or Crust

Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)

sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral

Gypsum (variety Selenite or Alabaster)

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Mineral

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Nephrite

Mineral/Rock