igneous
Snowflake Obsidian
Volcanic Glass with Spherulite inclusions (Chemical composition: 70–75% SiO2 + MgO, Fe3O4)
Hardness: 5-5.5 (Mohs scale), Color: Black with white or gray patches, Luster: Vitreous/Glassy, Crystal Structure: Amorphous (glass) with internal crystallites of Cristobalite, Cleavage: None (conchoidal fracture), Specific Gravity: 2.35–2.6
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Black with white or gray patches, Luster: Vitreous/Glassy, Crystal Structure: Amorphous (glass) with internal crystallites of Cristobalite, Cleavage: None (conchoidal fracture), Specific Gravity: 2.35–2.6
Formation & geological history
Formed through the rapid cooling of felsic (rhyolitic) lava. The 'snowflakes' are spherulitic inclusions formed as the glass begins to devitrify into Cristobalite over geological time. Usually associated with Cenozoic to Holocene volcanic activity.
Uses & applications
Commonly used for lapidary work, decorative cabochons for jewelry, pocket stones, and metaphysical sculptures. Historically used for making sharp blades and projectile points due to its conchoidal fracture.
Geological facts
Ancient cultures believed obsidian had protective properties. Unlike most rocks, obsidian is technically a 'mineraloid' because it is a supercooled liquid glass rather than a crystalline structure, though the snowflake patterns represent the start of crystallization.
Field identification & locations
Identify in the field by its distinct glassy black surface and white flower-like patches (spherulites). Found primarily in volcanic regions like Utah (USA), Mexico, and Iceland. Collectors look for high contrast and symmetrical patterns.
