mineral

Polished labradorite

Labradorite, CaAl₂Si₂O₈–NaAlSi₃O₈ (plagioclase feldspar)

AI-generated identification · may be incorrect

Mohs hardness 6–6.5; dark gray to black, glassy/vitreous luster, triclinic crystal structure, two cleavage directions, specific gravity about 2.68–2.72. The polished surface may show blue-green flash (labradorescence), though this specimen appears subdued.

Identified September 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms in mafic igneous rocks such as basalt, gabbro, and anorthosite through slow crystallization of feldspar-rich magma. Most labradorite is Precambrian to younger, with notable deposits in Canada, Madagascar, Finland, and Norway.

Uses & applications

Used for cabochons, tumbled stones, carvings, ornamental slabs, and collector specimens; large labradorite blocks are also used decoratively in architecture.

Geological facts

Its iridescence results from light interference in microscopic lamellae produced by exsolution within the feldspar crystal. Strong blue, green, or gold flash greatly increases desirability.

Field identification & locations

Identify by its dark feldspar appearance, moderate hardness, cleavage, and moving blue-green iridescence under directed light; distinguish it from obsidian by cleavage and lower glass-like uniformity. Common sources include Labrador, Canada, Madagascar, Finland, and Norway.