mineral

Feldspar (specifically Orthoclase)

Potassium Aluminum Silicate (KAlSi3O8)

AI-generated identification · may be incorrect

Hardness: 6 on Mohs scale; Color: Pink, reddish-peach, or white; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at nearly 90 degrees; Specific gravity: 2.55-2.63

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

Identified March 23, 2026More mineral →

Explore Feldspar (specifically Orthoclase) in the encyclopedia →

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: Pink, reddish-peach, or white; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at nearly 90 degrees; Specific gravity: 2.55-2.63

Formation & geological history

Formed primarily in igneous rocks like granite and pegmatite through the cooling of magma, as well as in metamorphic rocks like gneiss. They are among the most abundant minerals in Earth's crust across all geological eras.

Uses & applications

Used in the manufacture of glass and ceramics (porcelain), as a filler in paints and plastics, and as a mild abrasive. High-quality varieties like Moonstone or Sunstone are used in jewelry.

Geological facts

Feldspar makes up approximately 60% of the Earth's upper crust. The name is derived from the German 'Feldspat', meaning 'field spar' because of its prevalence in the ground.

Field identification & locations

Identify in the field by its characteristic blocky shape, pinkish hue, and the way it reflects light off its flat cleavage planes. It is commonly found in gravel, riverbeds, and mountainous granitic regions.