mineral

Orthoclase Feldspar

Potassium Feldspar (KAlSi3O8)

Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or tan; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two planes at right angles; Specific gravity: 2.55-2.63.

Hardness: 6 on Mohs scale
Color: Pink, salmon-orange, or tan
Luster: Vitreous to pearly

Identified July 5, 2026More mineral →

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Physical properties

Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or tan; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two planes at right angles; Specific gravity: 2.55-2.63.

Formation & geological history

Formed in igneous environments like granites and pegmatites, as well as in metamorphic rocks. It crystallizes from cooling magma at high temperatures.

Uses & applications

Used in the manufacturing of glass and ceramics (porcelain), as a filler in paints and plastics, and occasionally as a minor gemstone or decorative stone.

Geological facts

Orthoclase is one of the most common minerals in the Earth's crust. It is a defining mineral for number 6 on the Mohs hardness scale. The name comes from the Greek 'orthos' for straight and 'klasis' for fracture.

Field identification & locations

Identify by its distinctive pinkish/salmon color, 90-degree cleavage planes, and vitreous luster. Commonly found in granitic mountainous regions and riverbeds.