mineral

Orthoclase Feldspar

Orthoclase (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: 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: Pink, flesh-colored, or white
Luster: Vitreous to pearly

Identified May 31, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed as a primary constituent in igneous rocks like granite and syenite, as well as in pegmatites. It crystallizes from cooling magma and can also be found in metamorphic rocks.

Uses & applications

Used in the manufacture of glass, ceramics, and enamels. High-quality specimens like moonstone are used in jewelry.

Geological facts

Orthoclase is a major component of the Earth's crust. It is a defining mineral for level 6 on the Mohs scale of mineral hardness.

Field identification & locations

Identify by its light pink to salmon color and its distinctive 90-degree cleavage planes. Commonly found in granitic terrains globally, such as the Rocky Mountains or the Appalachian range.