igneous
Orthoclase (Potassium) Feldspar in Quartz
KAlSi3O8 (Potassium Aluminum Silicate)
Hardness: 6.0-6.5 on Mohs scale; Color: Pink, salmon-orange, to white; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.55-2.63.
- Hardness
- 6
- Color
- Pink, salmon-orange, to white
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6.0-6.5 on Mohs scale; Color: Pink, salmon-orange, to white; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.55-2.63.
Formation & geological history
Forms primarily in plutonic rocks like granite or pegmatites as magma cools slowly deep underground. This specific specimen appears water-worn (river rock), suggesting it was eroded from its source and tumbled in water over long geological periods.
Uses & applications
Used in the manufacture of glass and ceramics (porcelain), as a mild abrasive in scouring powders, and occasionally as a gemstone (if high quality like Moonstone).
Geological facts
Feldspar is the most abundant mineral group in the Earth's crust, making up about 60% of terrestrial rocks. The pink color is often due to trace amounts of hematite or iron within the crystal lattice.
Field identification & locations
Identify in the field by its distinct salmon-pink color, blocky cleavage planes, and hardness (it will scratch glass but cannot be scratched by a steel knife). Commonly found in mountain ranges or riverbeds near granitic outcrops.
