igneous
Snowflake Obsidian
Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)
Hardness: 5-5.5 on Mohs scale. Color: Black with white or grayish 'snowflake' patches. Luster: Vitreous (glassy). Crystal Structure: Amorphous (glassy) matrix with radial cristobalite crystals. Cleavage: None (conchoidal fracture). Specific Gravity: 2.35-2.6.
- Hardness
- 5-5
- Color
- Black with white or grayish 'snowflake' patches
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 on Mohs scale. Color: Black with white or grayish 'snowflake' patches. Luster: Vitreous (glassy). Crystal Structure: Amorphous (glassy) matrix with radial cristobalite crystals. Cleavage: None (conchoidal fracture). Specific Gravity: 2.35-2.6.
Formation & geological history
Formed from felsic lava that cools so rapidly that crystals do not have time to grow. The 'snowflakes' are inclusions of the mineral Cristobalite (a type of quartz) that formed as the glass began to devitrify over time.
Uses & applications
Predominantly used for ornamental purposes, jewelry (cabochons and beads), carvings, and as a popular specimen for rock collectors and metaphysical practitioners.
Geological facts
Despite having 'crystals' (the snowflakes), the black background is technically a liquid that never crystallized. Native Americans and other ancient cultures used variety of obsidian for tools and weapons due to its razor-sharp conchoidal fracture edges.
Field identification & locations
Identify by its distinct white radial patterns on a jet-black glassy surface. If chipped, it will show a curved, glass-like fracture. Commonly found in volcanic regions like Utah (USA), Mexico, and Iceland.
