Igneous

Black Obsidian

Volcanic Glass (SiO2 + impurities)

Hardness: 5-5.5 (Mohs); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6

Hardness: 5-5
Color: Jet black
Luster: Vitreous/Glassy

Identified March 25, 2026More igneous →

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Physical properties

Hardness: 5-5.5 (Mohs); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.35-2.6

Formation & geological history

Formed from extrusive igneous activity where felsic lava cools rapidly with minimal crystal growth. Found in volcanic regions of various ages, typically from the Cenozoic era due to its tendency to devitrify over time.

Uses & applications

Used for surgical scalpel blades, decorative cabochons, jewelry, stone tools (historically), and metaphysical collecting.

Geological facts

Ancient civilizations used obsidian for mirrors and razor-sharp weapons. It is technically a mineraloid, not a mineral, because it lacks a crystalline structure.

Field identification & locations

Identify by its glass-like texture, deep black color, and sharp, shell-like (conchoidal) edges when broken. Commonly found in the American West (Iceland, Mexico, Japan). Collectors look for uniform opacity and high polish.

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Fluorapatite (Ca5(PO4)3F)

mineral

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