igneous
Mahogany Obsidian
Volcanic glass (SiO2 with Hematite/Magnetite inclusions)
Hardness: 5-5.5 | Color: Dark brown or black with mahogany streaks | Luster: Vitreous/Glassy | Structure: Amorphous | Fracture: Conchoidal | Specific Gravity: 2.35-2.6
- Hardness
- 5-5
Identified More igneous →
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Physical properties
Hardness: 5-5.5 | Color: Dark brown or black with mahogany streaks | Luster: Vitreous/Glassy | Structure: Amorphous | Fracture: Conchoidal | Specific Gravity: 2.35-2.6
Formation & geological history
Formed when rhyolitic volcanic lava cools rapidly with minimal crystal growth. The mahogany coloration is caused by high concentrations of iron oxides (hematite) during the cooling process.
Uses & applications
Used primarily in lapidary work for cabochons, carvings, and tumbled stones. Historically used by various cultures to create sharp blades or arrowheads.
Geological facts
Because it is a volcanic glass and does not have a crystalline structure, it is technically a 'mineraloid' rather than a true mineral. The 'mahogany' nickname comes from its resemblance to dark mahogany wood.
Field identification & locations
Identify by its glassy texture and distinctive reddish-brown mottled pattern. Look for conchoidal (shell-like) fracture edges. Commonly found in areas of recent volcanic activity such as the United States (Oregon/California), Mexico, and Japan.
