igneous
Mahogany Obsidian
Volcanic glass containing Magnetite/Hematite
Hardness: 5-5.5 Mohs; Color: Brown to reddish-black with black inclusions; Luster: Vitreous/Glassy; Structure: Amorphous (Non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.3-2.6
- Hardness
- 5-5
- Color
- Brown to reddish-black with black inclusions
- Luster
- Vitreous/Glassy
Identified More igneous →
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Physical properties
Hardness: 5-5.5 Mohs; Color: Brown to reddish-black with black inclusions; Luster: Vitreous/Glassy; Structure: Amorphous (Non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.3-2.6
Formation & geological history
Formed from rapidly cooling silicic lava where cooling occurs too quickly for crystals to grow. The brown/red spots are caused by inclusions of Hematite or Magnetite. Found in Cenozoic volcanic regions.
Uses & applications
Used in gemstone carvings, cabochons for jewelry, ornamental objects, and holistic/metaphysical practices. Historically used for making sharp tools and arrowheads.
Geological facts
Unlike minerals, obsidian is a 'mineraloid' because it lacks a crystalline structure. Mahogany obsidian is known for its distinctive 'swirled' look which is unique to each piece based on how the minerals mixed in the lava.
Field identification & locations
Identified by its signature conchoidal (shell-like) fracture patterns and glassy texture. Commonly found in areas of recent volcanic activity such as Oregon and California, USA, and Mexico.
