igneous
Snowflake Obsidian
Volcanic Glass (spherulitic obsidian)
Hardness: 5-5.5 (Mohs scale), Color: Black with white or gray patches, Luster: Vitreous/Glassy, Structure: Amorphous (non-crystalline), Cleavage: None (Conchoidal fracture)
- 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, Structure: Amorphous (non-crystalline), Cleavage: None (Conchoidal fracture)
Formation & geological history
Formed when felsic lava cools rapidly, preventing crystal growth. The white patches (snowflakes) are inclusions of sphaerulite crystals, typically cristobalite, formed through devitrification.
Uses & applications
Used frequently in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for rock collectors and metaphysical practitioners.
Geological facts
Unlike most volcanic glass, the white patterns are actually caused by the slow crystallization of minerals within the glass over thousands of years. It was used historically for making sharp tools like arrows.
Field identification & locations
Identified by its distinctive 'snowflake' patches against a dark black glassy background. It is commonly found in areas with past volcanic activity like Utah, USA and Iceland.
