mineral

Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

Hardness: 6.0 on Mohs scale; Color: Pink, flesh-colored, to white; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.55-2.63

Hardness: 6
Color: Pink, flesh-colored, to white
Luster: Vitreous to pearly

Identified June 26, 2026More mineral →

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Physical properties

Hardness: 6.0 on Mohs scale; Color: Pink, flesh-colored, to white; 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 and extrusive igneous rocks such as granite and rhyolite. It crystallizes from magma and can also be found in metamorphic rocks like gneiss.

Uses & applications

Used extensively in the manufacture of glass and ceramics (porcelain, tiles); sometimes used as a mild abrasive in scouring powders; high-quality specimens are used as gemstones (e.g., Moonstone).

Geological facts

Feldspars are the most abundant group of minerals in the Earth's crust, making up about 60% of the terrestrial crust. The name comes from the German 'Feld', meaning field, and 'Spath', meaning a rock that does not contain ore.

Field identification & locations

Identify in the field by its distinct cream-to-pink color and its cleavage planes meeting at right angles. Commonly found in granitic pegmatites worldwide. Look for flat, shiny surfaces on broken edges.