igneous
Mahogany Obsidian
Obsidian (volcanic glass with hematite/magnetite inclusions)
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks/patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.4
- Hardness
- 5-5
- Color
- Black with reddish-brown streaks/patches
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks/patches; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.4
Formation & geological history
Formed through the extremely rapid cooling of felsic lava, preventing crystal growth. The reddish-brown 'mahogany' color is caused by high concentrations of iron oxides (hematite) or magnetite during the solidification process.
Uses & applications
Used in jewelry (beads, cabochons), ornamental carvings, and by collectors. Metaphysically, it is used as a 'grounding' stone. Historically used for making sharp blades and arrowheads.
Geological facts
Because it has no crystal structure, it is technically a 'mineraloid' rather than a mineral. It can be knapped to create a blade edge that is thinner and sharper than a surgical steel scalpel.
Field identification & locations
Identify by its glass-like texture and distinct conchoidal (shell-like) fracture patterns. Unlike pure black obsidian, it features swirling patches of brick-red. Found commonly in volcanic regions of the Western USA (Oregon, California), Mexico, and Japan.
