mineral
Blue-gray tumbled stone, likely labradorite or blue-gray feldspar
Plagioclase feldspar, possibly labradorite (NaAlSi₃O₈–CaAl₂Si₂O₈)
AI-generated identification · may be incorrectSmall rounded, polished specimen with blue-gray color, mottled darker inclusions, and a vitreous to subvitreous luster. Feldspar hardness is about 6–6.5 Mohs; cleavage is distinct in two directions, though obscured by tumbling. Identification is uncertain from the photograph alone.
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Physical properties
Small rounded, polished specimen with blue-gray color, mottled darker inclusions, and a vitreous to subvitreous luster. Feldspar hardness is about 6–6.5 Mohs; cleavage is distinct in two directions, though obscured by tumbling. Identification is uncertain from the photograph alone.
Formation & geological history
Plagioclase crystallizes mainly in igneous rocks such as basalt, gabbro, and anorthosite as magma cools. Its age depends on the source rock, ranging from geologically recent to billions of years old.
Uses & applications
Used as an ornamental and lapidary stone, especially when it displays labradorescence; feldspar is also important industrially in glass and ceramics.
Geological facts
Labradorite can show vivid blue, green, or gold flashes caused by light interference between microscopic feldspar layers. This specimen appears subdued and may instead be ordinary gray plagioclase or another tumbled silicate.
Field identification & locations
Look for blue iridescent flashes when tilted, feldspar cleavage, and hardness sufficient to scratch glass; confirm with a refractive-index or mineralogical test. Common sources include Labrador, Canada; Madagascar; Finland; and igneous terrains worldwide.
