igneous

Mahogany Obsidian Arrowhead

Volcanic Glass with Hematite/Magnetite inclusions (Amorphous Silicon Dioxide)

Hardness: 5-5.5 (Mohs scale); Color: Black with reddish-brown streaks or mottling; 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 or mottling
Luster: Vitreous (glassy)

Identified February 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the rapid cooling of rhyolitic lava which prevents crystal growth. The 'mahogany' coloring is caused by high concentrations of iron oxide (hematite or magnetite) impurities within the silica-rich melt. Typically found in volcanic regions from the Quaternary period.

Uses & applications

Used historically by indigenous peoples for tools and weaponry (arrowheads, knives) due to its sharp edges. Modernly used for lapidary work, jewelry, ornamental carvings, and metaphysical practices.

Geological facts

Obsidian is technically a supercooled liquid or mineraloid because it lacks a crystal lattice. Mahogany obsidian specifically gets its name from its similarity to mahogany wood grain. When napped properly, an obsidian edge can be many times sharper than a high-quality surgeon's steel scalpel.

Field identification & locations

Identify in the field by its distinct glassy luster and the circular, shell-like (conchoidal) fractures on the surface. Commonly found in areas with recent volcanic activity like Glass Buttes, Oregon, or various regions in Mexico. Collectors should look for patterns with high color contrast.

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Fluorapatite (Ca5(PO4)3F)

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Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Magnetite

Magnetite (Fe3O4)

mineral