Potassium Feldspar (Orthoclase)

Physical Properties

Hardness: 6 on Mohs scale; Color: Pinkish-orange (salmon); Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific Gravity: 2.55-2.63.

Formation & Geological History

Forms in igneous rocks like granite and syenite through the cooling of silica-rich magma; also found in metamorphic rocks (gneiss) and some sedimentary sandstones (arkose).

Uses & Applications

Used primarily in the manufacture of glass and ceramics (porcelain), as a filler in paints and plastics, and occasionally as a gemstone (moonstone variety).

Geological Facts

Feldspar is the most abundant mineral group in the Earth's crust. The pink color in this specimen is often caused by trace amounts of iron or hematite inclusions.

Field Identification & Locations

Identify in the field by its distinct salmon-pink color, blocky cleavage, and its ability to scratch glass but be scratched by a steel file. Commonly found in granitic mountainous regions.

Identified on: 5/10/2026

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