igneous
Polished obsidian (likely snowflake obsidian)
Volcanic glass, predominantly silica-rich rhyolite; snowflake obsidian contains cristobalite spherulites
AI-generated identification · may be incorrectBlack, glassy luster, conchoidal fracture, no visible crystal structure; Mohs hardness about 5–5.5. The pale patches may be surface reflections or snowflake-like inclusions, so the variety is uncertain from the photo.
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Physical properties
Black, glassy luster, conchoidal fracture, no visible crystal structure; Mohs hardness about 5–5.5. The pale patches may be surface reflections or snowflake-like inclusions, so the variety is uncertain from the photo.
Formation & geological history
Forms when silica-rich lava cools rapidly, preventing crystals from growing; obsidian is generally geologically young and occurs around volcanic flows and domes.
Uses & applications
Polished pieces are used for ornaments, jewelry, and collecting; historically, sharp flakes were used as cutting tools.
Geological facts
Obsidian is natural volcanic glass, not a mineral with a regular crystal lattice; its sharp fracture edges can be exceptionally keen.
Field identification & locations
Look for a glossy surface and curved, shell-like fracture; common sources include volcanic regions of the western United States, Mexico, Iceland, and Japan. The photographed piece appears cut or polished.
