igneous
Polished/tumbled labradorite (probable)
Labradorite-rich anorthosite or gabbro; plagioclase feldspar, approximately NaAlSi₃O₈–CaAl₂Si₂O₈
AI-generated identification · may be incorrectGray-green, rounded, fine- to medium-grained stone with dark mottling and possible weak blue-green labradorescence; vitreous to dull luster, Mohs hardness 6–6.5, specific gravity about 2.68–2.75, and two-directional feldspar cleavage. The photograph is not sufficient to confirm the mineral species.
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Physical properties
Gray-green, rounded, fine- to medium-grained stone with dark mottling and possible weak blue-green labradorescence; vitreous to dull luster, Mohs hardness 6–6.5, specific gravity about 2.68–2.75, and two-directional feldspar cleavage. The photograph is not sufficient to confirm the mineral species.
Formation & geological history
Crystallizes slowly from mafic magma in anorthosite or gabbroic plutons, commonly Precambrian in age (roughly 1–2 billion years for many famous deposits). Weathering and wave action can naturally round it; this specimen appears additionally polished or tumbled.
Uses & applications
Used as a lapidary stone, cabochon, bead, and collectible; labradorite slabs are also used decoratively. Ordinary pieces have modest value unless they show strong, broad blue or multicolor flash.
Geological facts
Labradorescence results from light interference within closely spaced plagioclase lamellae produced during cooling. The apparent stone could also be a related gabbro or weathered feldspathic pebble.
Field identification & locations
Look for gray feldspar, blocky cleavage, relatively high hardness, and blue-gold flash when rotated under a point light; a streak, fresh fracture, and refractive/index testing can distinguish it from gabbro or slag. Common sources include Labrador, Canada; Madagascar; Finland; Norway; and Russia.
