mineral

Orthoclase Feldspar

Orthoclase (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: Pink, flesh-colored, white, or salmon; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect at 90 degrees; Specific gravity: 2.55-2.63

Hardness: 6 on Mohs scale
Color: Pink, flesh-colored, white, or salmon
Luster: Vitreous to pearly

Identified March 7, 2026More mineral →

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, flesh-colored, white, or salmon; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect at 90 degrees; Specific gravity: 2.55-2.63

Formation & geological history

Formed through the cooling and crystallization of felsic (silica-rich) magmas in plutonic environments like batholiths. Commonly found in granitic pegmatites and metamorphic gneisses.

Uses & applications

Used primarily in the manufacture of glass and ceramics (porcelain), as a mild abrasive in scouring powders, and occasionally as a gemstone (moonstone variety).

Geological facts

Orthoclase is one of the ten defining minerals of the Mohs scale of mineral hardness. It is a major constituent of the Earth's continental crust and is the primary mineral that gives pink granite its distinctive hue.

Field identification & locations

Identify in the field by its distinct pink/salmon color, blocky cleavage (two planes meeting at 90 degrees), and inability to be scratched by a steel knife but ability to scratch glass. Found globally in granitic terrains.