igneous
Obsidian (Gold Sheen)
Obsidian (SiO2 + impurities)
Hardness: 5-5.5 on Mohs scale. Color: Black with a distinctive golden shimmer. Luster: Vitreous (glassy). Crystal structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture).
- Hardness
- 5-5
- Color
- Black with a distinctive golden shimmer
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 on Mohs scale. Color: Black with a distinctive golden shimmer. Luster: Vitreous (glassy). Crystal structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from extrusive volcanic activity where felsic lava cools rapidly with minimal crystal growth. The golden sheen is caused by tiny bubbles of gas trapped in the cooling glass, aligned along flow layers.
Uses & applications
Used primarily in jewelry, ornamental carvings, and holistic stone collections. Historically used for sharp cutting tools and scalpels due to its molecularly thin edge.
Geological facts
Obsidian is often called 'nature's glass'. Because it is amorphous and lacks a crystal structure, it is technically a mineraloid rather than a true mineral. The 'sheen' varieties are among the most sought after by collectors.
Field identification & locations
Identify by its glassy texture, conchoidal (shell-like) fracture patterns, and the chatoyant golden reflection visible when rotated under direct light. Found in volcanic regions like Mexico, Oregon, and Japan.
