mineral

Potassium Feldspar

Orthoclase (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or flesh-red; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63

Hardness: 6 on Mohs scale
Color: Pink, salmon-orange, or flesh-red
Luster: Vitreous to pearly

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or flesh-red; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63

Formation & geological history

Formed primarily in intrusive igneous rocks such as granite and syenite through the cooling of silica-rich magma; also appears in metamorphic rocks like gneiss and as a constituent in some sedimentary arkose sandstones.

Uses & applications

Extensively used in the manufacture of glass and ceramics (as a flux to lower melting points), as an abrasive in scouring powders, and occasionally as a semi-precious gemstone (Moonstone is a variety).

Geological facts

Feldspars make up roughly 60% of the Earth's crust. Potassium feldspar is the specific mineral that gives pink granite its distinctive color. It is a vital component in the Bowen's Reaction Series.

Field identification & locations

Identified in the field by its blocky habit, pink color, and 'right angle' cleavage planes. Found globally in continental crust areas, particularly the Appalachian Mountains, Rockies, and Scandinavian Shield.