igneous
Gold Sheen Obsidian
Volcanic Glass (Amorphous Silica with Magnetite inclusions)
Hardness: 5-5.5 (Mohs scale); Color: Black with a distinctive golden chatoyancy; Luster: Vitreous; Crystal Structure: Amorphous (glassy); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Black with a distinctive golden chatoyancy
- Luster
- Vitreous
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black with a distinctive golden chatoyancy; Luster: Vitreous; Crystal Structure: Amorphous (glassy); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
Formation & geological history
Formed from the rapid cooling of silica-rich rhyolitic lava. The golden sheen is caused by patterns of gas bubbles or microscopic inclusions of magnetite crystals oriented along the flow layers of the lava.
Uses & applications
Primarily used in jewelry making, ornamental carvings, lapidary art, and metaphysical collections.
Geological facts
Obsidian was historically used for making razor-sharp surgical scalpel blades and arrowheads because it breaks into pieces with edges thinner than high-quality steel.
Field identification & locations
Identify in the field by its glassy texture, shell-like (conchoidal) fracture, and the flash of gold when tilted under direct light. Common in volcanic regions such as Mexico, USA (Oregon, California), and Iceland.
