igneous

Black Obsidian

Obsidian (Volcanic Glass)

Hardness: 5-5.5 (Mohs scale); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.6

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

Identified May 3, 2026More igneous →

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Physical properties

Hardness: 5-5.5 (Mohs scale); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.6

Formation & geological history

Formed from rapid cooling of silica-rich (felsic) lava, preventing crystal growth. Usually found in geologically recent volcanic regions such as the Cascades or Rift Valleys.

Uses & applications

Used primarily in jewelry (beads, cabochons), ornamental carvings, and historical cutting tools. In modern medicine, it is sometimes used for ultra-sharp surgical scalpel blades.

Geological facts

Obsidian is technically an igneous rock but behaves like a mineral. It was highly prized in pre-Columbian Mesoamerica for creating weapons (Macuahuitl) due to its ability to break into edges thinner than steel.

Field identification & locations

Identify by its characteristic glassy luster and conchoidal (shell-like) fracture patterns. Frequently found in volcanic fields. Collectors look for high-gloss, uniform color and no visible air bubbles.

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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