Feldspar (Orthoclase)

Physical Properties

Hardness: 6 (Mohs scale), Color: Creamy white to pinkish-gray, 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 such as granite and pegmatite. It crystallizes from magma in various environments. It is one of the most abundant minerals in the Earth's crust, found in rocks dating back throughout the Phanerozoic and Precambrian eons.

Uses & Applications

Extensively used in the manufacture of glass and ceramics. Sometimes used as a gemstone (Moonstone) if high quality, or as an abrasive in scouring powders.

Geological Facts

Feldspar makes up about 60% of the Earth's crust. The name is derived from the German 'Feldspat', meaning 'field spar', a mineral that occurs in fields.

Field Identification & Locations

Identify in the field by its two-directional cleavage at right angles, its hardness (will scratch glass but be scratched by quartz), and light color. Found globally in granitic terrains and mountain ranges.

Identified on: 5/10/2026

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