igneous
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite inclusions (SiO2)
Hardness: 5-5.5 on Mohs scale; Color: Black with reddish-brown (mahogany) streaks or splotches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.6.
- Hardness
- 5-5
- Color
- Black with reddish-brown (mahogany) streaks or splotches
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 on Mohs scale; Color: Black with reddish-brown (mahogany) streaks or splotches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.6.
Formation & geological history
Formed from rhyolitic volcanic lava that cools rapidly, preventing crystal growth. The mahogany color is specifically caused by inclusions of Hematite or Magnetite during the cooling process.
Uses & applications
Commonly used for lapidary work, jewelry (beads, cabochons), ornamental carvings, and historical tool making (knapping). It is also highly popular in the metaphysical and collecting communities.
Geological facts
Despite having the composition of a mineral, obsidian is technically a volcanic glass because it lacks a crystalline structure. Ancient cultures used mahogany obsidian to make exceptionally sharp arrowheads and blades.
Field identification & locations
Identify by its glassy texture, smooth conchoidal (shell-like) fractures, and distinct reddish-brown swirls within a black base. It is commonly found in areas of recent volcanic activity, particularly in the Western USA, Mexico, and Japan.
