mineral

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: salmon pink to reddish-orange; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: two planes at 90 degrees; Specific gravity: 2.55-2.63

Hardness: 6 on Mohs scale
Color: salmon pink to reddish-orange
Luster: vitreous to pearly

Identified June 21, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6 on Mohs scale; Color: salmon pink to reddish-orange; Luster: vitreous to pearly; Crystal structure: Monoclinic; Cleavage: two planes at 90 degrees; Specific gravity: 2.55-2.63

Formation & geological history

Formed in igneous rocks like granite and pegmatites through slow cooling of magma. It is a primary constituent of the Earth's crust.

Uses & applications

Used in the manufacture of glass and ceramics, as a filler in paint and rubber, and occasionally as a gemstone (moonstone variant).

Geological facts

Orthoclase is one of the ten index minerals of 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.

Field identification & locations

Identify by its characteristic pink color and distinctive 90-degree cleavage planes. Commonly found in granitic mountain ranges worldwide.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

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