mineral
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or flesh-colored; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63
- Hardness
- 6 on Mohs scale
- Color
- Pink, salmon-orange, or flesh-colored
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6 on Mohs scale; Color: Pink, salmon-orange, or flesh-colored; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63
Formation & geological history
Formed primarily in igneous rocks like granite and syenite through the cooling of magma, as well as in metamorphic rocks like gneiss. It is a major component of the Earth's crust.
Uses & applications
Used in the manufacture of glass and ceramics (porcelain), as a filler in paints and plastics, and occasionally as a gemstone (Moonstone) if it exhibits opalescence.
Geological facts
Orthoclase is one of the ten defining minerals of the Mohs scale of mineral hardness. The name comes from the Greek for 'straight fracture,' referring to its two cleavage planes at right angles.
Field identification & locations
Identify in the field by its distinct pinkish color, 90-degree cleavage planes, and lack of striations (which distinguishes it from plagioclase feldspar). Commonly found in mountain ranges and crystalline shield areas.
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