mineral

Orthoclase (Potassium Feldspar)

KAlSi3O8 (Potassium Aluminum Silicate)

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

Identified March 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in granitic igneous rocks and pegmatites through the cooling of silica-rich magma; also appears in metamorphic rocks like gneiss. Originates throughout various geological ages from the Archaean to the Cenozoic.

Uses & applications

Extensively used in the manufacture of glass and ceramics (porcelain); used as a mild abrasive in scouring powders; occasionally used as a gemstone (moonstone variant) or for mineral collection.

Geological facts

Orthoclase is one of the ten defining minerals on the Mohs scale of mineral hardness. The name is derived from the Greek 'orthos' (right) and 'klasis' (fracture), referring to its two cleavage planes at right angles to each other.

Field identification & locations

Identify in the field by its blocky habit, pink/orange hue, and characteristic right-angle cleavage. Commonly found in granitic terrains worldwide, such as the Rocky Mountains, the Alps, and the Himalayas.

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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