igneous
Snowflake Obsidian
Volcanic Glass with Spherulite Inclusions (70–75% SiO2)
Hardness: 5–6 (Mohs scale); Color: Black with white or gray flower-like patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline glass); Fracture: Conchoidal; Specific Gravity: 2.4
- Hardness
- 5–6 (Mohs scale)
- Color
- Black with white or gray flower-like patches
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5–6 (Mohs scale); Color: Black with white or gray flower-like patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline glass); Fracture: Conchoidal; Specific Gravity: 2.4
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth. The 'snowflakes' are spherulites, composed of radiating needle-like crystals of cristobalite (a polymorph of silica) that formed as the glass devitrified over time.
Uses & applications
Primarily used for jewelry (beads, cabochons), ornamental carvings, crystal healing collections, and as a decorative landscaping stone.
Geological facts
Unlike most rocks, obsidian is technically a 'mineraloid' because it is a volcanic glass rather than a crystal. The white batches are actually a sign of the glass 'rotting' or devitrifying back into stable minerals.
Field identification & locations
Identify by its unique black glass appearance paired with distinct white, radiating patches. Commonly found in areas of recent volcanic activity such as Utah and Oregon (USA), Mexico, and Iceland. Collectors look for high contrast and well-defined flake patterns.
