igneous
Polished mahogany obsidian
Volcanic glass (mostly SiO₂), commonly called mahogany obsidian
AI-generated identification · may be incorrectHardness about 5–5.5 Mohs; dark reddish-brown to black, with a smooth vitreous/glassy luster and conchoidal fracture. It is noncrystalline (amorphous), lacks cleavage, and typically has specific gravity around 2.35–2.60.
Identified More igneous →
Explore Polished mahogany obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 5–5.5 Mohs; dark reddish-brown to black, with a smooth vitreous/glassy luster and conchoidal fracture. It is noncrystalline (amorphous), lacks cleavage, and typically has specific gravity around 2.35–2.60.
Formation & geological history
Rapid cooling of silica-rich rhyolitic lava prevented crystal growth, while iron-oxide inclusions produced the mahogany patches. Most deposits are Quaternary to relatively young Cenozoic volcanic materials.
Uses & applications
Used for ornamental carvings, cabochons, beads, polished specimens, and historically sharp tools and blades. Its value is primarily decorative and collectible rather than industrial.
Geological facts
Obsidian is natural volcanic glass, not a mineral in the strict crystallographic sense. The rounded rectangular object appears shaped and highly polished, possibly with a drilled or differently colored end.
Field identification & locations
Identify it by its glassy surface, conchoidal fracture, lack of visible crystals, and reddish-brown/black mottling; a glass-scratch test and examination of fresh edges can help, though the image alone is not definitive. Common sources include Oregon, Mexico, Arizona, Utah, and California.
