Rock Identifier
Tumbled labradorite bead strand (Labradorite, a plagioclase feldspar; approximately (Ca,Na)(Al,Si)₄O₈) — mineral
mineral

Tumbled labradorite bead strand

Labradorite, a plagioclase feldspar; approximately (Ca,Na)(Al,Si)₄O₈

AI-generated identification · may be incorrect

Dark gray to blue-purple, vitreous-to-pearly luster with iridescent labradorescence; Mohs hardness 6–6.5, triclinic crystals, two good cleavage directions, specific gravity about 2.68–2.72. The beads are polished and spherical, with visible blue flash.

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Physical properties

Dark gray to blue-purple, vitreous-to-pearly luster with iridescent labradorescence; Mohs hardness 6–6.5, triclinic crystals, two good cleavage directions, specific gravity about 2.68–2.72. The beads are polished and spherical, with visible blue flash.

Formation & geological history

Forms in slowly cooled mafic igneous rocks such as anorthosite, gabbro, and basaltic intrusions; commonly Precambrian, though younger occurrences exist. Iridescence results from light interference in microscopic exsolution lamellae within the feldspar.

Uses & applications

Used for beads, cabochons, carvings, and decorative objects; attractive material is popular in jewelry and mineral collecting. Typical strand value is about $15–$80, with stronger flash and larger beads reaching $100–$250.

Geological facts

Labradorescence is angle-dependent and may appear blue, green, gold, or violet. The specimen appears to be drilled, polished jewelry-grade material rather than a natural crystal.

Field identification & locations

Identify by dark body color, feldspar-like cleavage, moderate hardness, and shifting blue flash when tilted under directional light; common sources include Madagascar, Finland, Canada, and Norway. Avoid prolonged abrasion and harsh chemicals.