mineral

K-Feldspar (Potassium Feldspar)

Potassium Feldspar (KAlSi3O8)

Hardness: 6 on the Mohs scale; Color: Pink, reddish-brown, white, or gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic or triclinic; Cleavage: Two directions of good cleavage at approximately 90 degrees; Specific gravity: 2.5-2.6

Hardness: 6 on the Mohs scale
Color: Pink, reddish-brown, white, or gray
Luster: Vitreous to pearly

Identified July 30, 2026More mineral →

Explore K-Feldspar (Potassium Feldspar) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Forms commonly in igneous rocks such as granites, pegmatites, and syenites, as well as in metamorphic gneisses, through crystallization from cooling magma or high-temperature hydrothermal processes.

Uses & applications

Used primarily in the manufacturing of ceramics, glass, as a filler in paints and plastics, and occasionally as a minor gemstone or collector mineral specimen.

Geological facts

Feldspars are the most abundant group of minerals in the Earth's crust, making up about 60% of the crust. The distinctive pink or reddish color in potassium feldspar is often due to microscopic hematite inclusions.

Field identification & locations

Easily identified by its distinct pinkish-orange color, blocky crystal form, and two cleavage planes meeting near 90 degrees. Found worldwide in granitic terrains and pegmatite dykes.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Soil with Mineral Detritus and Quartz Fragments

Regolith / Silicate Mineral Aggregate

sedimentary

Limonite / Goethite (Iron Ore Mineral nodule)

FeO(OH)·nH2O / FeO(OH)

mineral

Schist

Metamorphic

Septarian Pebble

Septarian nodule / Concretion

sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral