mineral

Polished black labradorite heart

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

AI-generated identification · may be incorrect

Hardness 6–6.5 Mohs; dark gray to black body color with blue-green iridescent labradorescence, vitreous luster, and triclinic crystal structure. Cleavage is distinct in two directions; specific gravity is about 2.68–2.72.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms in mafic igneous rocks such as gabbro, anorthosite, and basalt as slowly cooled plagioclase. Most gem-quality material formed in Precambrian to Mesozoic intrusive bodies, especially in Madagascar, Finland, Canada, and Norway.

Uses & applications

Used for cabochons, carvings, hearts, beads, and ornamental stone; large slabs may be used decoratively. Value depends mainly on vivid, broad flashes and minimal fractures.

Geological facts

Its color play results from light interference within microscopic exsolution layers of feldspar, not surface coating. Spectral colors shift with viewing angle and are strongest when polished.

Field identification & locations

Identify it by rotating the specimen under a strong light: genuine labradorite shows directional blue, green, gold, or multicolor flashes within a gray-black stone. A glassy uniform appearance without angular color change may indicate imitation.