mineral
Polished labradorite cabochons
Labradorite, calcium-rich plagioclase feldspar (approximately (Ca,Na)(Al,Si)₄O₈)
AI-generated identification · may be incorrectDark gray to black, polished, with gray-blue iridescent flashes (labradorescence); hardness 6–6.5 Mohs, vitreous luster, triclinic crystal structure, two good cleavage directions, specific gravity about 2.68–2.72.
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Physical properties
Dark gray to black, polished, with gray-blue iridescent flashes (labradorescence); hardness 6–6.5 Mohs, vitreous luster, triclinic crystal structure, two good cleavage directions, specific gravity about 2.68–2.72.
Formation & geological history
Forms in mafic igneous rocks such as basalt, gabbro, and anorthosite as magma cools; most specimens formed during Precambrian to younger geological episodes. These pieces are cut and polished cabochons.
Uses & applications
Used for jewelry, carvings, cabochons, decorative stone, and collectors’ specimens; attractive blue or multicolor flash increases value.
Geological facts
Labradorescence results from light interference within microscopic exsolution layers in the feldspar, not from surface coating.
Field identification & locations
Identify by gray-black body color, cleavage, moderate hardness, and shifting blue-green-gold flash when tilted under a point light; major sources include Madagascar, Finland, Canada, Norway, and Russia.
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