mineral

Orthoclase Feldspar

Potassium Aluminum Silicate (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: Flesh-pink to salmon-red (as seen here) or white/cream; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90-degree angles; Specific gravity: 2.55-2.63.

Hardness: 6 on Mohs scale
Color: Flesh-pink to salmon-red (as seen here) or white/cream
Luster: Vitreous to pearly

Identified March 2, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Commonly forms in igneous rocks like granite and pegmatites through the cooling and crystallization of magma. It can also form in metamorphic rocks through regional metamorphism.

Uses & applications

Primarily used in the glass and ceramics industries as a flux to lower melting points. It is also used in mild abrasives (like scouring powder) and occasionally as a gemstone (moonstone variant).

Geological facts

Orthoclase is one of the ten defining minerals 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 salmon-pink color, blocky cleavage patterns, and its inability to be scratched by a steel knife (hardness 6). Found worldwide in granitic terrains.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral