igneous
Snowflake Obsidian
Obsidian with Cristobalite inclusions (mostly amorphous SiO2)
Hardness: 5-6 Mohs. Color: Black with white-gray 'snowflake' patches. Luster: Vitreous/glassy. Crystal structure: Amorphous (non-crystalline) with spherulitic inclusions of cristobalite. Cleavage: None (conchoidal fracture).
- Hardness
- 5-6 Mohs
- Color
- Black with white-gray 'snowflake' patches
- Luster
- Vitreous/glassy
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Physical properties
Hardness: 5-6 Mohs. Color: Black with white-gray 'snowflake' patches. Luster: Vitreous/glassy. Crystal structure: Amorphous (non-crystalline) with spherulitic inclusions of cristobalite. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the rapid cooling of silica-rich felsic lava, preventing crystal growth. The 'snowflakes' are a result of devitrification, where the volcanic glass begins to crystallize into cristobalite (a polymorph of quartz) in radial patterns.
Uses & applications
Primarily used for ornamental purposes, jewelry (pendants, beads), tumbled stones for collecting, and metaphysical uses. Historically, obsidian was used for sharp cutting tools and arrowheads.
Geological facts
Snowflake obsidian is technically a volcanic glass rather than a mineral. The 'snowflakes' are called spherulites. While regular obsidian is completely amorphous, these patches represent the rock's slow transition from a glass to a crystalline solid over geological time.
Field identification & locations
Identify by its glassy black base and distinct, flower-like or snowflake-patterned white inclusions. Commonly found in volcanic regions such as Utah (USA), Mexico, and Iceland. For collectors, look for high contrast between the black glass and white inclusions.
