igneous
Snowflake Obsidian (Tumbled)
Obsidian with Cristobalite inclusions
Hardness: 5-5.5. Color: Black with white or gray 'snowflake' patches. Luster: Vitreous/glassy. Crystal structure: Amorphous (glass) with crystalline inclusions. Cleavage: None, conchoidal fracture.
- Hardness
- 5-5
- Color
- Black with white or gray 'snowflake' patches
- Luster
- Vitreous/glassy
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Physical properties
Hardness: 5-5.5. Color: Black with white or gray 'snowflake' patches. Luster: Vitreous/glassy. Crystal structure: Amorphous (glass) with crystalline inclusions. Cleavage: None, conchoidal fracture.
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth. The 'snowflakes' are spherulites of the mineral cristobalite, a high-temperature quartz polymorph, which formed as the glass began to slowly crystallize over time.
Uses & applications
Commonly used in lapidary, jewelry making (cabochons, beads), and as pocket stones or ornamental objects. Historically used for making sharp tools and arrowheads before being tumbled.
Geological facts
The presence of cristobalite 'snowflakes' indicates that the obsidian is beginning to devitrify (turn from glass to crystal). This process takes millions of years, meaning snowflake obsidian is generally older than pure black obsidian.
Field identification & locations
Identify by its distinctive black base with white, snowflake-like patterns. Typically found in areas with past volcanic activity, such as the western United States (Utah is a notable source). When tumbling, the softer glass may wear slightly differently than the cristobalite.
