mineral
Polished star-shaped gemstone, likely black obsidian
Obsidian (volcanic glass), predominantly SiO₂
AI-generated identification · may be incorrectBlack, opaque, and vitreous with no visible crystals; Mohs hardness about 5–5.5, conchoidal fracture, and specific gravity about 2.35–2.65. The star shape is human-cut and polished, not a natural crystal form.
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Physical properties
Black, opaque, and vitreous with no visible crystals; Mohs hardness about 5–5.5, conchoidal fracture, and specific gravity about 2.35–2.65. The star shape is human-cut and polished, not a natural crystal form.
Formation & geological history
Obsidian forms when silica-rich lava cools so rapidly that crystals cannot grow, generally in volcanic regions younger than several million years. The specimen has been shaped and polished by human processing.
Uses & applications
Used for carvings, ornamental objects, jewelry, cutting tools, and collectibles; it has little construction value in this form.
Geological facts
Obsidian is technically a natural glass rather than a crystalline mineral. Asterism or star-shaped carving should not be confused with naturally occurring star crystals.
Field identification & locations
Identify it by uniform black glassy appearance, sharp conchoidal edges, and lack of grain or cleavage; common sources include Mexico, the western United States, Armenia, and Turkey. Exact identification is uncertain from the backlit image and could include black glass or another dark stone.
