igneous
Mahogany Obsidian
Volcanic glass (Silicon Dioxide with Hematite/Magnetite inclusions)
Hardness: 5-5.5; Color: Reddish-brown with black streaks; Luster: Vitreous/glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.3-2.6
- Hardness
- 5-5
- Color
- Reddish-brown with black streaks
- Luster
- Vitreous/glassy
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Physical properties
Hardness: 5-5.5; Color: Reddish-brown with black streaks; Luster: Vitreous/glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.3-2.6
Formation & geological history
Formed when rhyolitic lava cools rapidly, preventing crystal growth. The mahogany coloration comes from high concentrations of inclusions, usually hematite or magnetite, occurring in flow patterns during the cooling process.
Uses & applications
Used primarily for jewelry (cabochons), polished decorative stones, energetic/metaphysical collecting, and historically for sharp tools and arrowheads.
Geological facts
Unlike minerals, obsidian is a 'mineraloid' because it lacks a crystal structure. Mahogany obsidian specifically contains iron-rich impurities that create the distinct reddish-brown swirls within the black glass matrix.
Field identification & locations
Identify by its glassy texture, smooth conchoidal (shell-like) fractures, and distinct mahogany-brown and black color banding. It is commonly found in volcanic regions of Mexico, the United States (Oregon, California), and Japan.
