igneous
Black Obsidian
Volcanic Glass (Amorphous Silicon Dioxide)
Hardness: 5-5.5 | Color: Deep black, opaque to translucent | Luster: Vitreous/Glassy | Structure: Amorphous (non-crystalline) | Cleavage: None, exhibits perfect conchoidal (shell-like) fracture
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 | Color: Deep black, opaque to translucent | Luster: Vitreous/Glassy | Structure: Amorphous (non-crystalline) | Cleavage: None, exhibits perfect conchoidal (shell-like) fracture
Formation & geological history
Formed by the rapid cooling of silica-rich (felsic) lava, which prevents the growth of crystals. It is found in geologically recent volcanic fields or older locations where it hasn't devitrified.
Uses & applications
Historically used for blades and arrowheads; currently used in jewelry, meditation stones, interior decor, and specialized surgical scalpels due to its sharpness at the molecular level.
Geological facts
Obsidian can be fractured to create an edge many times sharper than high-quality steel tools. It is not technically a mineral because it lacks a crystalline structure; it is a mineraloid.
Field identification & locations
Identify by its smooth, glassy surface and sharp, curved fracture patterns. Commonly found in volcanic regions of Mexico, the United States (Oregon, California), Iceland, and Italy.
