igneous
Snowflake obsidian
Volcanic glass (silica-rich rhyolitic composition), commonly with cristobalite inclusions
AI-generated identification · may be incorrectTypically black, glassy, and opaque with white-to-gray radial “snowflake” patterns; hardness about 5–5.5 Mohs, conchoidal fracture, no cleavage, and specific gravity around 2.3–2.6. The specimen appears tumbled and polished.
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Physical properties
Typically black, glassy, and opaque with white-to-gray radial “snowflake” patterns; hardness about 5–5.5 Mohs, conchoidal fracture, no cleavage, and specific gravity around 2.3–2.6. The specimen appears tumbled and polished.
Formation & geological history
Forms when silica-rich lava cools rapidly into natural volcanic glass; the snowflakes are commonly spherulitic cristobalite or feldspar-rich crystallization zones. It is generally Quaternary to younger than surrounding volcanic formations.
Uses & applications
Used for cabochons, beads, carvings, polished stones, and decorative objects; occasionally used in ornamental stonework. It has modest collector value rather than high gemstone value.
Geological facts
Obsidian is not technically a crystal because rapid cooling prevents extensive crystal growth. Its conchoidal fracture can produce extremely sharp edges.
Field identification & locations
Identify by its smooth glassy luster, black base, curved fracture, and distinctive pale snowflake patches; common sources include Mexico, Oregon, Utah, and California. Avoid confusing it with slag or dyed glass.
