igneous
Snowflake Obsidian
Volcanic glass containing Spherulite inclusions (primarily Cristobalite, SiO2)
Hardness: 5-5.5 on Mohs scale. Color: Black with white-to-gray 'snowflake' patches. Luster: Vitreous/Glassy. Structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture).
- Hardness
- 5-5
- Color
- Black with white-to-gray 'snowflake' patches
- Luster
- Vitreous/Glassy
Identified More igneous →
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Physical properties
Hardness: 5-5.5 on Mohs scale. Color: Black with white-to-gray 'snowflake' patches. Luster: Vitreous/Glassy. Structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the rapid cooling of felsic (silica-rich) lava. The 'snowflakes' are spherulite inclusions formed when the glass undergoes partial devitrification, allowing the mineral cristobalite to grow in radiating needle-like patterns.
Uses & applications
Commonly used in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for metaphysical crystal collecting. Historically used for making sharp tools and arrowheads.
Geological facts
Despite being an igneous rock, it is biologically described as a 'glass' because it cools so quickly that crystals cannot form in the matrix. The 'snowflakes' are one of the few instances where crystallization occurs within the cooling glass after formation.
Field identification & locations
Identify by its distinct white patches on a deep black, glassy surface. Common locations include volcanic regions in Utah (USA), Mexico, and Iceland. Collectors should look for sharp conchoidal edges on raw pieces and a high-gloss finish on tumbled stones.
