igneous

Mahogany Obsidian

Volcanic Glass with Hematite inclusions (SiO2 + Fe2O3)

Hardness: 5-5.5; Color: Black with reddish-brown streaks; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.3 - 2.6.

Hardness: 5-5
Color: Black with reddish-brown streaks
Luster: Vitreous/Glassy

Identified March 30, 2026More igneous →

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Physical properties

Hardness: 5-5.5; Color: Black with reddish-brown streaks; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.3 - 2.6.

Formation & geological history

Formed through the rapid cooling of silica-rich rhyolitic lava. The mahogany color is produced by high concentrations of iron oxides (magnetite or hematite) trapped within the glass. Specimens can range from thousands to millions of years old.

Uses & applications

Commonly used in lapidary arts for cabochons, beads, and decorative carvings. Historically used for making sharp tools like scrapers and arrowheads. Also popular in the metaphysical market as a grounding stone.

Geological facts

Because it is natural glass and lacks an internal crystalline structure, it is technically a 'mineraloid' rather than a true mineral. It is often found in the vicinity of standard black obsidian flows.

Field identification & locations

Identify by its distinctive glassy sheen and brick-red to brown swirling patterns over a black base. It is frequently found in volcanic regions of the Western United States (Oregon, California, Utah) and Mexico. Collectors should look for unique banding or patterns.

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Igneous

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