igneous

Mahogany Obsidian

Volcanic glass (high silica) with inclusions of Magnetite or Hematite

Hardness: 5-5.5; Color: Brown/Reddish-brown with black swirls/streaks; Luster: Vitreous (glassy); Crystal Structure: Amorphous; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3-2.6

Hardness: 5-5
Color: Brown/Reddish-brown with black swirls/streaks
Luster: Vitreous (glassy)

Identified June 3, 2026More igneous →

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Physical properties

Hardness: 5-5.5; Color: Brown/Reddish-brown with black swirls/streaks; Luster: Vitreous (glassy); Crystal Structure: Amorphous; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3-2.6

Formation & geological history

Formed from the rapid cooling of silica-rich rhyolitic lava. The reddish color comes from inclusions of iron-rich minerals like hematite or magnetite trapped during formation.

Uses & applications

Used primarily in lapidary work for jewelry, decorative carvings, and as a grounding stone in metaphysical practices. Historically used for sharp tools.

Geological facts

Unlike minerals, obsidian is a 'mineraloid' because it cooled too quickly for crystals to grow. It is essentially glass formed by a volcano.

Field identification & locations

Identify by its glass-like texture and characteristic wavy reddish-brown and black patterns. Common in volcanic regions like the American West (Oregon, California) and Mexico.

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Magnetite

Iron(II,III) oxide (Fe3O4)

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Dark Igneous Rock (Likely Basalt or Diabase)

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Igneous