igneous
Mahogany Obsidian
Volcanic Glass (with inclusions of Magnetite or Hematite)
Hardness: 5.0-5.5 on Mohs scale; Color: Reddish-brown to black with wavy or spotted patterns; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.60
- Hardness
- 5
- Color
- Reddish-brown to black with wavy or spotted patterns
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5.0-5.5 on Mohs scale; Color: Reddish-brown to black with wavy or spotted patterns; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.60
Formation & geological history
Formed when felsic lava high in silica cools extremely rapidly, preventing crystal growth. Its mahogany color comes from high concentrations of iron oxide and hematite. It can be found in volcanic regions spanning millions of years to recent history.
Uses & applications
Used primarily for lapidary work, jewelry making (cabochons and beads), ornamental carvings, and historical sharp tools/weapons. It is also a popular specimen for rock collection and metaphysical uses.
Geological facts
Mahogany Obsidian is unique because it is technically a glass rather than a mineral. In ancient times, obsidian was prized more for its ability to be flaked into blades sharper than steel than for its beauty.
Field identification & locations
Identify by its glass-like texture, conchoidal (shell-like) fracture patterns, and distinctive dark 'blobs' of brown iron oxide within a black or tan background. Commonly found in Oregon (USA), Mexico, and volcanic areas of Japan.
