igneous
Mahogany Obsidian
Volcanic Glass with Hematite/Magnetite (SiO2 + Fe2O3)
Hardness: 5–5.5 Mohs. Color: Black with reddish-brown streaks or mottling. Luster: Vitreous (glassy). Crystal Structure: Amorphous. Cleavage: None (conchoidal fracture). Specific Gravity: 2.35–2.60.
- Hardness
- 5–5
- Color
- Black with reddish-brown streaks or mottling
- Luster
- Vitreous (glassy)
Identified More igneous →
Explore Mahogany Obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5–5.5 Mohs. Color: Black with reddish-brown streaks or mottling. Luster: Vitreous (glassy). Crystal Structure: Amorphous. Cleavage: None (conchoidal fracture). Specific Gravity: 2.35–2.60.
Formation & geological history
Formed through the rapid cooling of felsic lava, preventing mineral crystallization. The distinctive mahogany color is caused by the inclusion of iron oxides (hematite or magnetite) during the cooling process in volcanic environments.
Uses & applications
Primarily used in jewelry (beads, cabochons), ornamental carvings, and holistic stone collecting. Historically used for making sharp tools like arrows and scrapers due to its conchoidal fracture.
Geological facts
Despite looking like a mineral, obsidian is actually a volcanic glass. Mahogany obsidian is rarer than pure black obsidian and is highly prized for its unique undulating patterns that look like wood grain.
Field identification & locations
Identify by its glass-like texture and red-brown swirls against a black background. Commonly found in areas with recent volcanic activity such as the Western USA (Oregon, California), Mexico, and Japan. Best identified by its smooth, sharp edges when broken.
