mineral

Orthoclase Feldspar

Potassium aluminum silicate (KAlSi3O8)

Hardness: 6 (Mohs), Color: Pinkish-orange/tan, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Two planes at 90 degrees, Specific gravity: 2.55-2.63

Identified March 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 (Mohs), Color: Pinkish-orange/tan, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Two planes at 90 degrees, Specific gravity: 2.55-2.63

Formation & geological history

Formed through the cooling and crystallization of felsic magmas and in metamorphic rocks. Commonly found in granitic pegmatites.

Uses & applications

Major industrial ingredient in the manufacture of glass and ceramics (porcelain and glazes). Gem-quality varieties like moonstone are used in jewelry.

Geological facts

Orthoclase is one of the most common minerals in the Earth's crust. It is a defining mineral for level 6 on the Mohs scale of mineral hardness.

Field identification & locations

Identify in the field by its distinct pinkish/flesh color and 90-degree cleavage planes. It is abundant in continental mountain ranges and riverbeds containing granitic gravel.

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