igneous
Mahogany Obsidian
Obsidian (volcanic glass with Hematite/Magnetite inclusions)
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks or mottling; Luster: Vitreous (glassy); Crystal structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.3 - 2.6.
- Hardness
- 5-5
- Color
- Black with reddish-brown streaks or mottling
- Luster
- Vitreous (glassy)
Identified More igneous →
Explore Mahogany Obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks or mottling; Luster: Vitreous (glassy); Crystal structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific gravity: 2.3 - 2.6.
Formation & geological history
Formed when rhyolitic magma cools rapidly upon reaching the Earth's surface, preventing crystal growth. The mahogany color is specifically caused by high concentrations of iron oxide (Hematite or Magnetite) within the molten glass during solidification.
Uses & applications
Used primarily in lapidary work for cabochons, carvings, and beads. Historically used for sharp tools/knives. In modern times, it is used for jewelry, metaphysical palm stones, and decorative objects.
Geological facts
Mahogany obsidian is essentially natural glass. Despite its dark appearance, it is often chemically more similar to granite than basalt. Its edges can be sharp down to a molecular level, and it has been used in antiquity for surgical scalpels.
Field identification & locations
Identify in the field by its distinct glassy texture and scallop-shaped (conchoidal) fractures. The 'mahogany' patches are irregular. Common locations include Oregon and California (USA), Mexico, and Japan.
