mineral

Plagioclase Feldspar

NaAlSi3O8 – CaAlSi2O8 (Sodium-Calcium Aluminum Silicates)

AI-generated identification · may be incorrect

Hardness: 6.0 – 6.5 on Mohs scale; Color: White to gray; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Two distinct directions nearly at 90 degrees; Specific gravity: 2.6 – 2.8

Hardness: 6
Color: White to gray
Luster: Vitreous to pearly

Identified March 31, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling and crystallization of igneous rocks (both intrusive and extrusive), as well as in metamorphic rocks. It is a primary constituent of Earth's crust across various geological ages.

Uses & applications

Used in the manufacture of glass and ceramics as a flux; also crushed for road aggregate and construction material. High-quality specimens with labradorescence (like Moonstone) are used in jewelry.

Geological facts

Feldspars are the most abundant mineral group on Earth, making up about 60% of the crust. This specific specimen shows typical 'twinning' striations on cleavage surfaces that are characteristic of the plagioclase series.

Field identification & locations

Identify in the field by its distinct white-to-pearly color and its rectangular cleavage planes. Look for tiny parallel grooves (striations) on the flat surfaces which distinguish it from Potassium Feldspar. Commonly found in granite, diorite, and gabbro.