igneous
Tumbled mahogany obsidian (likely)
Volcanic glass, predominantly silica-rich rhyolitic glass; exact variety uncertain from image
AI-generated identification · may be incorrectSmooth, rounded, glossy orange-brown specimen with dark patches, consistent with polished mahogany obsidian. Obsidian is typically Mohs 5–5.5, noncrystalline, and lacks cleavage; this small image does not show diagnostic fracture surfaces.
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Physical properties
Smooth, rounded, glossy orange-brown specimen with dark patches, consistent with polished mahogany obsidian. Obsidian is typically Mohs 5–5.5, noncrystalline, and lacks cleavage; this small image does not show diagnostic fracture surfaces.
Formation & geological history
Forms when silica-rich lava cools rapidly, preventing crystal growth; the geological age depends on its volcanic source. Brown-red and black patterning commonly results from iron-rich inclusions or devitrification.
Uses & applications
Often tumbled for jewelry, ornaments, and collecting; obsidian has also been used historically for sharp cutting tools.
Geological facts
Obsidian breaks with a curved, shell-like (conchoidal) fracture and can form exceptionally sharp edges.
Field identification & locations
The glossy surface and dark-brown patches suggest mahogany obsidian, but identification is uncertain without closer inspection; similar jasper or other iron-stained stones can look alike. Obsidian occurs near volcanic deposits, including in the western United States, Mexico, and parts of the Mediterranean.
