igneous
Snowflake Obsidian
Volcanic glass with Phenocrysts (SiO2)
Hardness: 5-5.5 (Mohs), Color: Black with grayish-white snowflake-like patches, Luster: Vitreous/Glassy, Structure: Amorphous (glass) with spherulite inclusions, Cleavage: None/Conchoidal fracture, SG: 2.35-2.6.
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs), Color: Black with grayish-white snowflake-like patches, Luster: Vitreous/Glassy, Structure: Amorphous (glass) with spherulite inclusions, Cleavage: None/Conchoidal fracture, SG: 2.35-2.6.
Formation & geological history
Formed when felsic lava cools rapidly with minimal crystal growth, though the 'snowflakes' are spherulites of cristobalite (a silica polymorph) formed through partial devitrification.
Uses & applications
Used extensively in jewelry for beads and cabochons, ornamental carvings, and 'healing' stones in metaphysical practices.
Geological facts
Unlike most rocks, obsidian is actually a volcanic glass. The white patches (snowflakes) are radiating needle-like crystals of the mineral cristobalite.
Field identification & locations
Identify by its glassy black surface and distinctive white spots. Found in volcanic regions including Utah (USA), Mexico, and Iceland. Noted for its conchoidal (shell-like) fracture edges which can be extremely sharp.
