igneous
Snowflake Obsidian
Volcanic glass containing Spherulites (SiO2)
Hardness: 5-5.5 (Mohs scale), Color: Black with white or gray patches, Luster: Vitreous/Glassy, Crystal Structure: Amorphous (glassy) with cristobalite inclusions, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.35-2.6
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Black with white or gray patches, Luster: Vitreous/Glassy, Crystal Structure: Amorphous (glassy) with cristobalite inclusions, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.35-2.6
Formation & geological history
Formed from rapidly cooling rhyolitic lava. The 'snowflakes' are spherulites, which are radial clusters of needle-like cristobalite crystals that form as the glass begins to devitrify.
Uses & applications
Used in jewelry (cabochons, beads), decorative carvings, meditation stones, and as a collector's specimen.
Geological facts
Snowflake obsidian is unique because it represents a stage of 'aging' for volcanic glass; over geological time, most obsidian will eventually crystallize completely. It was historically used for making sharp tools and arrowheads.
Field identification & locations
Identify by its distinctive white 'snowflake' patches against a jet-black glassy background. It is commonly found in volcanic regions of the United States (Utah, Oregon), Mexico, and Iceland.
