gemstone

Polished labradorite cabochon (probable)

Labradorite, calcium-rich plagioclase feldspar; approximately (Ca,Na)(Al,Si)₄O₈

AI-generated identification · may be incorrect

Hardness 6–6.5 Mohs; dark gray to blue body color with vivid blue-green schiller (labradorescence), vitreous luster, triclinic crystal structure, and two good cleavage directions. The image is dim and slightly blurred, so identification is approximate.

Identified September 7, 2026More gemstone →

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Physical properties

Formation & geological history

Forms in mafic igneous rocks such as gabbro, anorthosite, and basalt through crystallization of plagioclase magma, commonly in Precambrian terrains. Gem-quality material is especially associated with Madagascar, Finland, Canada, Norway, and Russia.

Uses & applications

Used for cabochons, beads, carvings, and ornamental slabs; also used as a decorative architectural stone. It is generally unsuitable for high-abrasion jewelry because of cleavage and moderate hardness.

Geological facts

Its blue flash results from light interference within fine, compositionally layered plagioclase lamellae, not from surface coating. Strong color play is called labradorescence.

Field identification & locations

Identify by rotating the polished surface under directional light: flashes should move across the stone while the base remains gray or blue-gray; glass imitations lack this feldspar cleavage and natural internal structure.