igneous
Mahogany Obsidian
Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions
Hardness: 5-5.5 (Mohs); Color: Dark brown or reddish-brown with black spots; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Dark brown or reddish-brown with black spots
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 (Mohs); Color: Dark brown or reddish-brown with black spots; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6
Formation & geological history
Formed through the extremely rapid cooling of felsic lava, preventing crystal growth. Its reddish-brown color is caused by the inclusion of iron-rich minerals like hematite or magnetite during the cooling process. Usually found in geologically recent volcanic areas (Cenozoic era).
Uses & applications
Commonly used in jewelry, lapidary arts (cabochons and beads), and decorative carvings. Historically, obsidian was used for sharp cutting tools and surgical blades; currently popular in the metaphysical and gemstone collecting markets.
Geological facts
Obsidian is often called 'volcanic glass.' While it looks like a mineral, it is technically an 'extrusive igneous rock' because it lacks a crystalline structure. The 'Mahogany' variety is prized for its wavy, wood-grain-like patterns.
Field identification & locations
Identify by its glass-like texture, conchoidal (shell-like) fracture patterns, and its distinct red-and-black mottling. Commonly found in volcanic regions of the Western United States (Oregon, California), Mexico, and Japan.
