mineral

Feldspar

KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8

Hardness: 6.0-6.5 Mohs. Color: White, pink, gray, or salmon. Luster: Vitreous to pearly. Crystal structure: Monoclinic or Triclinic. Cleavage: Perfect in two directions at 90 degrees.

Hardness: 6
Color: White, pink, gray, or salmon
Luster: Vitreous to pearly

Identified May 9, 2026More mineral →

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Physical properties

Hardness: 6.0-6.5 Mohs. Color: White, pink, gray, or salmon. Luster: Vitreous to pearly. Crystal structure: Monoclinic or Triclinic. Cleavage: Perfect in two directions at 90 degrees.

Formation & geological history

Forms in igneous rocks like granite and basalt, metamorphic rocks like gneiss, and some sedimentary sandstones. Found globally across all geological ages as it makes up 60% of Earth's crust.

Uses & applications

Used in the manufacture of glass and ceramics, as a filler in paint and rubber, and in some scouring powders. Gemstone varieties like Moonstone or Sunstone are used in jewelry.

Geological facts

Feldspar is the most abundant mineral group in the Earth's crust. It is often used by geologists to determine the age of rocks through argon-argon dating.

Field identification & locations

Identify in the field by its distinct cleavage planes that reflect light and its hardness which can scratch glass but is scratched by quartz. Common in granitic terrains.