igneous
Black Obsidian
Obsidian (Volcanic Glass), primarily SiO2 (Silicon Dioxide) with impurities
Hardness: 5–5.5 on Mohs scale; Color: Jet black to dark gray; Luster: Vitreous (glass-like); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.4
- Hardness
- 5–5
- Color
- Jet black to dark gray
- Luster
- Vitreous (glass-like)
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Physical properties
Hardness: 5–5.5 on Mohs scale; Color: Jet black to dark gray; Luster: Vitreous (glass-like); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.4
Formation & geological history
Formed through the rapid cooling of felsic lava, preventing crystal growth. Most specimens found today are relatively young geologically (Cenozoic to Holocene) as the glass eventually devitrifies into quartz and feldspar over millions of years.
Uses & applications
Used for making jewelry, scalpels for precision surgery due to its molecularly sharp edges, ornamental carvings, and 'scrying' stones in metaphysical communities.
Geological facts
Because it lacks a crystal structure, obsidian edges can reach near-molecular thinness, making it sharper than high-quality steel scalpels. It was used by ancient civilizations for weaponry, such as the Aztec Macuahuitl.
Field identification & locations
Identify by its smooth, glassy surface and characteristic curved (conchoidal) fractures that resemble ripples in water. Commonly found in volcanic regions such as the American Northwest, Mexico, Iceland, and Italy.
