igneous
Polished black obsidian with a possible snowflake/vein inclusion
Volcanic glass; mainly rhyolitic silica glass (SiO₂), potentially with cristobalite or mineral inclusions
AI-generated identification · may be incorrectTypically black to brown, vitreous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5. The specimen is tumbled/polished, with reflective gray-white internal patches or fractures and a brown translucent edge.
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Physical properties
Typically black to brown, vitreous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5. The specimen is tumbled/polished, with reflective gray-white internal patches or fractures and a brown translucent edge.
Formation & geological history
Obsidian forms when silica-rich lava cools so rapidly that crystals cannot grow, generally during Quaternary to recent volcanic eruptions. Common sources include volcanic fields in the western United States, Mexico, Armenia, Iceland, and Japan.
Uses & applications
Used for carvings, jewelry, cabochons, ornamental objects, and historically exceptionally sharp cutting tools. It is valued mainly as a decorative lapidary material.
Geological facts
Its glassy fracture can produce edges sharper than surgical steel, though they are brittle. The visible pattern may reflect devitrification, mineral inclusions, or healed fractures rather than true snowflake obsidian.
Field identification & locations
Identify by its glassy appearance, conchoidal fracture, sharp edges, and lack of visible crystal grains; it should not fizz with acid or show metallic magnetism. Common polished pieces usually sell for $5–$25; unusual patterns or larger quality cabochons may bring $30–$100.
