mineral

Polished labradorite

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

AI-generated identification · may be incorrect

Typically gray to dark blue-black with blue-green iridescent flashes (labradorescence), vitreous luster, triclinic crystals, two excellent cleavage directions, Mohs hardness 6–6.5, and specific gravity about 2.68–2.72. The rounded, glossy form indicates it has been tumbled or polished.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Forms in mafic igneous rocks such as basalt, gabbro, and anorthosite as magma cools; most deposits are Precambrian to younger. Its optical flash results from light interference in microscopic exsolution layers within the feldspar.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and mineral collections; rarely used as an architectural stone. Jewelry value depends strongly on flash intensity, color, pattern, and lack of fractures.

Geological facts

Labradorescence is not ordinary surface color but a structural optical effect caused by internal lamellae. Strong electric-blue or multicolor flash is especially desirable.

Field identification & locations

Identify it by gray body color, polished surface, and directional blue flashes that change with viewing angle; common sources include Madagascar, Finland, Canada, Norway, and Mexico. Avoid ultrasonic cleaning and harsh impacts because cleavage can cause splitting.