Mineral

Plagioclase Feldspar

Plagioclase Feldspar Series (NaAlSi3O8 - CaAl2Si2O8)

Hardness: 6 to 6.5. Color: Usually white, gray, or colorless; can be pink or green. Luster: Vitreous (glassy). Crystal structure: Triclinic. Cleavage: Two directions at nearly 90 degrees. Key feature: Parallel fine lines (striations) on some cleavage surfaces.

Hardness: 6 to 6
Color: Usually white, gray, or colorless
Luster: Vitreous (glassy)

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the crystallization of magma or lava in igneous environments, as well as in high-grade metamorphic rocks. They are common in both intrusive rocks like granite and extrusive rocks like basalt.

Uses & applications

Used widely in the ceramics and glass manufacturing industry as a flux. Labradorite varieties are popular as gemstones and decorative counter-tops. Also used as a generic aggregate in road construction.

Geological facts

Feldspars make up approximately 60% of the Earth's crust. Some varieties, like Labradorite or Moonstone, exhibit a stunning play-of-color phenomenon known as labradorescence or adularescence.

Field identification & locations

Identify in the field by looking for the twin lamellae (parallel striations) on cleavage planes which distinguish it from potassium feldspar. Commonly found in mountain ranges and volcanic zones globally.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

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)]

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Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral