Mineral/Igneous (Volcanic Glass)
Mahogany Obsidian or Red Jasper
Silicon Dioxide with Iron Oxide (SiO2+Fe2O3)
Hardness: 5-7 (Mohs scale), Color: Reddish-brown with black inclusions, Luster: Vitreous to waxy, Crystal Structure: Amorphous (non-crystalline) or Microcrystalline, Cleavage: Conchoidal fracture, Specific Gravity: 2.35 - 2.6
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Physical properties
Hardness: 5-7 (Mohs scale), Color: Reddish-brown with black inclusions, Luster: Vitreous to waxy, Crystal Structure: Amorphous (non-crystalline) or Microcrystalline, Cleavage: Conchoidal fracture, Specific Gravity: 2.35 - 2.6
Formation & geological history
Formed from the rapid cooling of silica-rich lava (rhyolitic) that cools too quickly for crystals to grow. Iron inclusions create the mahogany/reddish hues. Commonly found in Tertiary to Holocene volcanic fields.
Uses & applications
Used primarily in jewelry (cabochons, beads), decorative carvings, and alternative healing practices. Historically used for making sharp cutting tools like arrowheads and knives.
Geological facts
Mahogany Obsidian is unique because its needle-like inclusions of hematite or magnetite create the distinct reddish-brown swirls. It has been used by humans for over 10,000 years for weaponry due to its ability to fracture into razor-sharp edges.
Field identification & locations
Identify by its glassy luster and smooth, curved (conchoidal) fractures. Typically found in volcanic regions such as the American Northwest (Oregon, California), Mexico, and Japan. Collectors look for high contrast between the red and black patterns.
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