igneous
Mahogany Obsidian
Volcanic Glass with Hematite inclusions
Hardness: 5-5.5 (Mohs), Color: Dark brown to black with reddish-brown streaks/spots, Luster: Vitreous (glassy), Structure: Amorphous (non-crystalline), Specific Gravity: 2.3-2.6
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs), Color: Dark brown to black with reddish-brown streaks/spots, Luster: Vitreous (glassy), Structure: Amorphous (non-crystalline), Specific Gravity: 2.3-2.6
Formation & geological history
Formed through the rapid cooling of rhyolitic volcanic lava. The mahogany color is produced by high concentrations of iron oxide (hematite) or magnetite during the solidification process.
Uses & applications
Commonly used for lapidary work, jewelry (beads, cabochons), ornamental carvings, and holistic uses. Historically used for making sharp tools like scrapers and arrowheads.
Geological facts
Unlike most rocks, obsidian is not a mineral because it lacks a crystalline structure; it is considered a mineraloid. The red-brown swirls are often called 'mahogany' due to their resemblance to the wood grain.
Field identification & locations
Can be identified in the field by its conchoidal (shell-like) fracture and glassy texture. Common locations include the United States (specifically Oregon and California), Mexico, and Japan.
