igneous
Snowflake obsidian cabochon
Obsidian (volcanic glass), SiO₂-rich; white areas are cristobalite/spherulitic devitrification
AI-generated identification · may be incorrectBlack, glassy, noncrystalline matrix with contrasting white radial “snowflakes”; hardness about 5–5.5 Mohs, conchoidal fracture, no cleavage, specific gravity about 2.35–2.60. The specimen is polished and likely shaped as a cabochon.
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Physical properties
Black, glassy, noncrystalline matrix with contrasting white radial “snowflakes”; hardness about 5–5.5 Mohs, conchoidal fracture, no cleavage, specific gravity about 2.35–2.60. The specimen is polished and likely shaped as a cabochon.
Formation & geological history
Forms when silica-rich lava cools rapidly, preventing crystal growth; white spherulites develop as the glass partially devitrifies. Most natural obsidian is Quaternary to younger, associated with volcanic fields.
Uses & applications
Used for jewelry, ornaments, cabochons, and decorative objects; historically knapped into exceptionally sharp tools and weapon points.
Geological facts
Snowflake patterns are not frost but radiating mineral-growth structures, commonly cristobalite or feldspar-rich spherulites within volcanic glass.
Field identification & locations
Identify by its glossy black glass, sharp conchoidal fracture, and white flower-like patches; common sources include Oregon, Utah, California, Mexico, and Armenia. Avoid confusing it with dyed glass or slag.
