igneous
Black Obsidian
Obsidian (Volcanic Glass, SiO2+)
Hardness: 5.0-5.5 (Mohs scale), Color: Jet black, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.35-2.60
- Hardness
- 5
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Physical properties
Hardness: 5.0-5.5 (Mohs scale), Color: Jet black, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.35-2.60
Formation & geological history
Formed through the rapid cooling of silica-rich (felsic) lava. The cooling occurs so quickly that crystals do not have time to grow, resulting in a natural volcanic glass. Specimens can date from any period of active volcanic history.
Uses & applications
Used for making scalpel blades (sharper than steel), jewelry, decorative gemstone carvings, and 'scrying' stones in metaphysical communities. Historically used for arrowheads and tools.
Geological facts
Obsidian is technically a mineraloid rather than a mineral because it lacks a crystalline structure. It is extremely sharp when broken; its edges can reach molecular thinness.
Field identification & locations
Identify by its glass-like texture and characteristic shell-like (conchoidal) fractures. Found in volcanic regions like Iceland, Mexico, and the Western United States. Polished 'tumbled' versions are very smooth and opaque black.
