mineral

Feldspar (specifically Orthoclase)

Potassium aluminum silicate (KAlSi3O8)

Hardness: 6.0 on Mohs scale; Color: typically salmon-pink to reddish-brown; Luster: vitreous to pearly; Crystal structure: monoclinic; Cleavage: perfect in two directions at 90 degrees.

Hardness: 6
Color: typically salmon-pink to reddish-brown
Luster: vitreous to pearly

Identified June 25, 2026More mineral →

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Physical properties

Hardness: 6.0 on Mohs scale; Color: typically salmon-pink to reddish-brown; Luster: vitreous to pearly; Crystal structure: monoclinic; Cleavage: perfect in two directions at 90 degrees.

Formation & geological history

Formed in igneous rocks like granite and rhyolite, as well as metamorphic rocks like gneiss. It crystallizes from cooling magma at high temperatures and is the most abundant mineral group in the Earth's crust.

Uses & applications

Used in the manufacture of glass and ceramics (porcelain), as a filler in paints and plastics, and occasionally as a gemstone (sunstone or moonstone varieties).

Geological facts

Feldspar makes up about 60% of the Earth's crust. The name comes from the German 'Feldspat', meaning 'field spar' because it was often found in fields.

Field identification & locations

Identify in the field by its blocky shape, salmon-pink color, and flat cleavage planes that reflect light evenly. It is harder than glass but can be scratched by quartz.

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