igneous
Snowflake Obsidian
Spherulitic Obsidian (Amorphous Volcanic Glass with Cristobalite inclusions)
Hardness: 5-5.5 (Mohs scale), Color: Black with greyish-white radial patterns, Luster: Vitreous to dull (when unpolished), Structure: Amorphous (non-crystalline glass with mineral inclusions), Fractures: Conchoidal
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Black with greyish-white radial patterns, Luster: Vitreous to dull (when unpolished), Structure: Amorphous (non-crystalline glass with mineral inclusions), Fractures: Conchoidal
Formation & geological history
Formed when felsic lava cools too rapidly for crystal growth, becoming volcanic glass. The 'snowflakes' consist of cristobalite (a type of quartz) that grew through devitrification over time. Common in areas with high volcanic activity like Utah, Mexico, and Iceland.
Uses & applications
Commonly used for ornamental carvings, jewelry (cabochons and beads), and as a gemstone in metaphysical collections. Historically used for sharp tools or blades due to its sharp conchoidal fracture.
Geological facts
Unlike most stones, obsidian is not actually a mineral because it is volcanic glass and lacks a crystalline structure. The 'snowflakes' are a result of the glass beginning to crystallize into silicates like cristobalite.
Field identification & locations
Identify by the distinct white blossoming patterns on a jet black background. Look for the sharp edges and glass-like texture. Common in the Western USA, particularly the Black Rock Desert of Utah.
