igneous
Mahogany Obsidian
Volcanic glass (SiO2 with Hematite or Magnetite inclusions)
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks or mottling; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.35-2.6
- Hardness
- 5-5
- Color
- Black with reddish-brown streaks or mottling
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks or mottling; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.35-2.6
Formation & geological history
Formed from rhyolitic volcanic eruptions where the lava cools rapidly, preventing crystal growth. The mahogany color comes from inclusions of Hematite or Magnetite during the cooling process. Common in volcanic regions from the Holocene to Pleistocene epochs.
Uses & applications
Used in jewelry (beads, cabochons), ornamental carvings, stone tools (due to its sharpness when fractured), and metaphysical collecting.
Geological facts
Obsidian fractures with edges so sharp that they are sometimes used in surgical scalpels because they cause less tissue trauma than steel. Mahogany obsidian specifically gets its name from its resemblance to mahogany wood.
Field identification & locations
Identify in the field by its distinct glassy texture and conchoidal (shell-like) fracture patterns. It is predominantly found in the Western United States (Oregon, California), Mexico, and Japan.
