mineral

Plagioclase Feldspar

Plagioclase (NaAlSi3O8 - CaAl2Si2O8)

AI-generated identification · may be incorrect

Hardness: 6-6.5 Mohs; Color: White to grey; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Two directions at nearly 90 degrees; Specific gravity: 2.62-2.76.

Hardness: 6-6
Color: White to grey
Luster: Vitreous to pearly

Identified June 30, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs; Color: White to grey; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Two directions at nearly 90 degrees; Specific gravity: 2.62-2.76.

Formation & geological history

Forms in igneous rocks like basalt, granite, and diorite as magma cools, as well as in metamorphic rocks. It is archaic, dating back to the formation of the Earth's crust.

Uses & applications

Used in the ceramics and glass industry to improve durability and resistance. Some varieties like moonstone or labradorite are used in jewelry. Also used as an aggregate in construction.

Geological facts

Feldspars are the most abundant mineral group in the Earth's crust. Plagioclase is a solid solution series ranging from sodium-rich albite to calcium-rich anorthite.

Field identification & locations

Identify in the field by its white color, hardness (greater than steel), and the presence of fine, parallel grooves called polysynthetic twinning striations on cleavage surfaces.