igneous
Snowflake Obsidian
Volcanic glass (SiO2 - Silicon Dioxide with Cristobalite inclusions)
Hardness: 5-5.5 on Mohs scale; Color: Black with white or grey 'snowflakes'; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35–2.6
- Hardness
- 5-5
- Color
- Black with white or grey 'snowflakes'
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 on Mohs scale; Color: Black with white or grey 'snowflakes'; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35–2.6
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth, but specifically when localized devitrification occurs. The 'snowflakes' are inclusions of the mineral cristobalite, a types of quartz, that formed as the glass began to crystallize over time. Found in volcanic regions ranging from prehistoric to several million years old.
Uses & applications
Primarily used for jewelry (cabochons, beads, pendants), ornamental carvings, and 'healing' stones in metaphysical practices. Historically, obsidian was used for making extremely sharp cutting tools/scalpels.
Geological facts
Despite being considered a mineraloid because it lacks a crystal structure, it contains radially grown crystals called spherulites (the snowflakes). It is often associated with the 'balance' of light and dark in folklore.
Field identification & locations
Identified by its jet-black glassy base and distinctive white flower-like patches. In the field, look for conchoidal (shell-like) fracturing and sharp edges. Common locations: USA (Utah, California), Mexico, and Iceland.
