Obsidian
rock · common
Quick facts
- Formula
- SiO2-rich volcanic glass
- Hardness
- 5–5.5
- Luster
- Vitreous
- Colors
- Black, mahogany, snowflake
Felsic volcanic glass. Conchoidal fracture, very sharp edges, no crystal structure.
Not a mineral. Snowflake obsidian contains cristobalite spherulites.
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