mineral

Feldspar

Potassium Feldspar (KAlSi3O8)

Hardness: 6.0 on the Mohs scale; Color: White to off-white/pale cream; Luster: Vitreous to pearly; Crystal structure: Monoclinic or Triclinic; Cleavage: Two planes at right angles; Specific gravity: 2.55-2.63

Hardness: 6
Color: White to off-white/pale cream
Luster: Vitreous to pearly

Identified May 24, 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

Formed through the crystallization of magma in both intrusive and extrusive igneous rocks, as well as in high-grade metamorphic rocks and as a constituent in some sedimentary rocks. They represent the most abundant mineral group in the Earth's crust.

Uses & applications

Used in the manufacture of glass and ceramics, as a filler in paint and plastics, and as an abrasive in scouring cleansers. Translucent varieties like Moonstone are used in jewelry.

Geological facts

Feldspar makes up about 60% of the Earth's crust. The name comes from the German words 'Feld' (field) and 'Spath' (a rock that does not contain ore).

Field identification & locations

Identify in the field by its blocky shape, two cleavage planes meeting at nearly 90 degrees, and its hardness (it will scratch glass but not quartz). Found worldwide, especially in granitic landscapes.