igneous
Snowflake Obsidian
Obsidian (volcanic glass) with Cristobalite inclusions
Hardness: 5-5.5 on Mohs scale; Color: Black with white to grayish 'snowflake' patches; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline) with crystalline spherulites; Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6.
- Hardness
- 5-5
- Color
- Black with white to grayish 'snowflake' patches
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 on Mohs scale; Color: Black with white to grayish 'snowflake' patches; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline) with crystalline spherulites; Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6.
Formation & geological history
Formed from rapidly cooling felsic lava where water and gas are present. The 'snowflakes' are formed by the process of devitrification, where the amorphous glass begins to crystallize into radiates of cristobalite spherulites. Found in volcanic regions ranging from the Tertiary to Holocene periods.
Uses & applications
Primarily used for jewelry (cabochons, beads), decorative carvings, and as a popular lapidary material for hobbyists and collectors.
Geological facts
Obsidians have been used since prehistoric times to make razor-sharp tools and weapons. Snowflake obsidian is unique because it represents the 'un-making' of a glass as it slowly attempts to turn into stable crystals over geological time.
Field identification & locations
Identify in the field by its distinct glass-like shell-shaped (conchoidal) fractures and the presence of white, star-shaped patterns on a black background. Commonly found in volcanic areas such as the Western United States (Utah, Oregon), Mexico, and Iceland.
