igneous
Polished mahogany obsidian
Obsidian, natural volcanic glass (mostly SiO₂)
AI-generated identification · may be incorrectDark reddish-brown with black patches and a glossy polish; glassy, noncrystalline structure, no cleavage, Mohs hardness about 5–5.5. The image alone cannot confirm the identification; similar jasper or iron-rich rocks are possible.
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Physical properties
Dark reddish-brown with black patches and a glossy polish; glassy, noncrystalline structure, no cleavage, Mohs hardness about 5–5.5. The image alone cannot confirm the identification; similar jasper or iron-rich rocks are possible.
Formation & geological history
Forms when silica-rich lava cools rapidly, preventing crystals from growing; typically associated with geologically recent volcanic activity.
Uses & applications
Used for carvings, jewelry, decorative objects, and historically for sharp tools.
Geological facts
Mahogany obsidian’s reddish-brown areas result from iron-bearing inclusions or oxidation within the volcanic glass.
Field identification & locations
Obsidian is commonly found near volcanic fields, including parts of the western United States, Mexico, and Iceland. A glassy surface and curved, shell-like fracture are useful clues; this specimen’s polish obscures diagnostic fracture features.
