mineral

Orthoclase Feldspar

KAlSi3O8 (Potassium aluminum silicate)

AI-generated identification · may be incorrect

Hardness: 6 on Mohs scale; Color: typically salmon-pink to 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: typically salmon-pink to flesh-red
Luster: Vitreous to pearly

Identified May 7, 2026More mineral →

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Physical properties

Hardness: 6 on Mohs scale; Color: typically salmon-pink to flesh-red; 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 igneous rocks like granite and syenite through the cooling of magma, as well as in metamorphic rocks like gneiss. It is a major component of the Earth's continental crust.

Uses & applications

Used in the manufacture of glass and ceramics (porcelain); sometimes used as a mild abrasive in scouring powders; gem-quality varieties like moonstone are used in jewelry.

Geological facts

Orthoclase is one of the index minerals for level 6 on the Mohs scale of mineral hardness. The name is derived from the Greek for 'straight fracture', referring to its two cleavage planes at right angles to each other.

Field identification & locations

Identify in the field by its distinct pinkish-orange color, 90-degree cleavage planes, and hardness (it can scratch glass but is scratched by quartz). Commonly found in granitic batholiths and pegmatites worldwide.