mineral

Potassium Feldspar (Orthoclase / Microcline)

KAlSi3O8 (Potassium Aluminum Silicate)

Hardness: 6 on Mohs scale. Color: Pinkish-orange, salmon, to brownish-pink. Luster: Vitreous to pearly on cleavage surfaces. Cleavage: Two directions meeting at nearly 90 degrees. Specific gravity: 2.56-2.59.

Hardness: 6 on Mohs scale
Color: Pinkish-orange, salmon, to brownish-pink
Luster: Vitreous to pearly on cleavage surfaces

Identified July 25, 2026More mineral →

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

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Physical properties

Formation & geological history

Formed as a major constituent of intrusive igneous rocks such as granites and pegmatites through slow cooling of silicate magma, as well as in high-grade metamorphic rocks.

Uses & applications

Widely used in the manufacture of ceramics, glass, enamel, and abrasives. High-grade aesthetic specimens or moonstone varieties are used as gemstones and in mineral collections.

Geological facts

Feldspars make up over 50% of Earth's crust. Potassium feldspar is defined as the defining mineral for hardness 6 on Friedrich Mohs' scale of mineral hardness.

Field identification & locations

Identified in the field by its distinctive pink/salmon color, blocky cleavage fragments, hardness that scratches glass but is scratched by quartz, and pearly luster on flat cleavage planes. Very common worldwide in granite regions.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

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)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock