igneous
Black obsidian bead bracelet
Obsidian — natural volcanic glass, chiefly silicic SiO₂-rich composition
AI-generated identification · may be incorrectTypically black, vitreous and strongly reflective, with no visible crystals or cleavage; hardness about 5–5.5 Mohs and specific gravity about 2.3–2.6. The beads are polished and shaped, so surface appearance is not entirely natural.
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Physical properties
Typically black, vitreous and strongly reflective, with no visible crystals or cleavage; hardness about 5–5.5 Mohs and specific gravity about 2.3–2.6. The beads are polished and shaped, so surface appearance is not entirely natural.
Formation & geological history
Forms when silica-rich lava cools so rapidly that crystals cannot develop, usually in Quaternary volcanic settings. Common sources include Mexico, the western United States, Armenia, Ethiopia, and Japan.
Uses & applications
Used for beads, ornaments, carvings, and historically extremely sharp cutting tools; it is not generally used as structural construction stone. Jewelry value depends on polish, uniformity, provenance, and whether the material is genuine obsidian.
Geological facts
Obsidian fractures conchoidally and can produce edges sharper than many steel blades. Black obsidian may contain microscopic gas bubbles, flow bands, or subtle sheen; some similar black beads are glass, onyx, or dyed stone.
Field identification & locations
Identify by its glassy luster, conchoidal fracture, opaque black body, and lack of granular crystals; a streak, hardness, or microscopic examination can help distinguish it from glass. This processed bracelet is commonly worth about $10–$40, or $50–$150 for high-quality, provenance-rich material.
