mineral

Plagioclase Feldspar

Plagioclase (NaAlSi3O8 - CaAl2Si2O8 series)

Hardness: 6-6.5 (Mohs scale); Color: White, gray, or colorless; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Two directions at nearly 90 degrees; Specific Gravity: 2.62-2.76; Appearance: Displays characteristic striations on cleavage planes.

Hardness: 6-6
Color: White, gray, or colorless
Luster: Vitreous to pearly

Identified June 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the crystallization of magma or lava in igneous rocks like basalt, andesite, and diorite. It also occurs in metamorphic rocks through recrystallization processes. It is one of the most common minerals in the Earth's crust.

Uses & applications

Used in the manufacture of glass and ceramics, as a building stone (dimension stone), and as a filler in plastics and paint. Some aesthetic varieties like Labradorite or Moonstone are used in jewelry.

Geological facts

Feldspar minerals make up about 60% of the Earth's outer crust. The white or gray stripes visible on the surface are called 'polysynthetic twinning' or 'albite law striations,' which are a primary diagnostic feature.

Field identification & locations

Identify in the field by looking for the rectangular cleavage and fine, parallel grooves (striations) on the flat surfaces. Most common in mountain ranges and volcanic zones globally. Collectors should look for flashes of color (labradorescence) in certain varieties.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

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metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral