mineral

Potassium Feldspar

Orthoclase (KAlSi3O8)

Hardness: 6.0 on Mohs scale; Color: Pink to salmon-orange; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63

Hardness: 6
Color: Pink to salmon-orange
Luster: Vitreous to pearly

Identified June 28, 2026More mineral →

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Physical properties

Hardness: 6.0 on Mohs scale; Color: Pink to salmon-orange; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63

Formation & geological history

Forms primarily in felsic igneous rocks like granite and pegmatites through the cooling of magma, as well as in high-grade metamorphic rocks. Common in the Canadian Shield region.

Uses & applications

Used in the manufacture of glass and ceramics (porcelain), as a mild abrasive in scouring powders, and occasionally as a gemstone (moonstone variant).

Geological facts

Orthoclase is one of the ten defining minerals of the Mohs scale of mineral hardness. It is the most common mineral in the Earth's crust after quartz.

Field identification & locations

Identified by its pinkish/flesh color and distinct blocky cleavage at nearly right angles. Common in the glacial till and bedrock of Southern Ontario near Mississauga/Toronto.