igneous
Snowflake Obsidian
Volcanic Glass with Cristobalite Inclusions (SiO2)
Hardness: 5 to 5.5 on the Mohs scale; Color: Black with white or grey snowflake-like patches; Luster: Vitreous (glassy); Crystal structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.35 to 2.45
- Hardness
- 5 to 5
- Color
- Black with white or grey snowflake-like patches
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5 to 5.5 on the Mohs scale; Color: Black with white or grey snowflake-like patches; Luster: Vitreous (glassy); Crystal structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.35 to 2.45
Formation & geological history
Formed when felsic lava extruded from a volcano cools rapidly with little crystal growth, followed by the partial devitrification of the glass over time, causing cristobalite minerals to grow in radial snowflake patterns known as spherulites.
Uses & applications
Used primarily in lapidary arts, tumbled stones, crystal healing, ornamental carvings, and historical cutting tools such as arrowheads and blades.
Geological facts
Obsidian has been used by humans since the Stone Age for sharp implements. The 'snowflakes' are actually clusters of tiny white cristobalite crystals growing within the dark volcanic glass.
Field identification & locations
Easily identified by its distinctive black-and-white patterned appearance and glossy luster. Found in areas with past volcanic activity such as the United States, Mexico, Iceland, and Italy.
