igneous
Mahogany Obsidian
Obsidian (Volcanic Glass) with Hematite/Magnetite inclusions
Hardness: 5.0-5.5 on Mohs scale; Color: Black with reddish-brown streaks; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6.
- Hardness
- 5
- Color
- Black with reddish-brown streaks
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5.0-5.5 on Mohs scale; Color: Black with reddish-brown streaks; Luster: Vitreous (glassy); Crystal Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6.
Formation & geological history
Formed from the rapid cooling of silica-rich (rhyolitic) lava, which prevents crystal growth. The mahogany color comes from magnetite or hematite inclusions during the cooling process, typically found in volcanic fields varying from thousands to millions of years old.
Uses & applications
Used primarily in lapidary for making beads, cabochons, and jewelry. It is also highly popular in 'crystal healing' communities and as a display specimen for collectors.
Geological facts
Obsidian was historically used to make some of the sharpest cutting tools and arrowheads in human history. Mahogany obsidian is chemically similar to black obsidian but differs due to the oxidation of iron within the glass during its formation.
Field identification & locations
Identify in the field by its distinctive glassy, rippled (conchoidal) surface and reddish-brown mottling. It is commonly found in the United States (Oregon, California, Utah), Mexico, and Japan.
