igneous
Snowflake Obsidian
Obsidian with Cristobalite inclusions (Amorphous SiO2 + SiO2 inclusions)
Hardness: 5-5.5 (Mohs scale); Color: Black with white or grey splotches; Luster: Vitreous (glassy); Crystal structure: Amorphous (volcanic glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Black with white or grey splotches
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black with white or grey splotches; Luster: Vitreous (glassy); Crystal structure: Amorphous (volcanic glass); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth, but over time, partial devitrification occurs where certain areas crystallize into sphaerulites of the mineral cristobalite. Typically found in Cenozoic volcanic regions.
Uses & applications
Predominantly used for jewelry (beads, cabochons), ornamental carvings, and by collectors for its aesthetic 'snowflake' patterns.
Geological facts
The white 'snowflakes' are actually radial clusters of cristobalite, a type of quartz. While obsidian is technically a volcanic glass and not a mineral, it is a significant geological material used since the Stone Age for tools.
Field identification & locations
Identify in the field by its glassy texture, shell-like (conchoidal) fractures, and distinctive white radial patches against a jet-black background. Commonly found in areas with recent volcanic activity like Utah, USA, and Mexico.
