igneous

Obsidian

Volcanic Glass (Amorphous Silica)

Hardness: 5-5.5 (Mohs scale); Color: Black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.60.

Hardness: 5-5
Color: Black
Luster: Vitreous/Glassy

Identified May 8, 2026More igneous →

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Physical properties

Hardness: 5-5.5 (Mohs scale); Color: Black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.35-2.60.

Formation & geological history

Obsidian is an extrusive igneous rock formed when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. It is found in volcanic regions from the Tertiary to Quaternary geological periods.

Uses & applications

Historically used for scalpels and tools due to sharp edges; currently used for ornamental beads, jewelry, gemstones, and decorative sculptures.

Geological facts

Obsidian is technically a glass rather than a mineral because it lacks a crystalline structure. It is so sharp that some surgeons use obsidian scalpels for precision incisions because they leave less scarring than steel.

Field identification & locations

Identified by its shiny, black, glassy appearance and conchoidal (shell-like) fracture patterns. Frequently found in volcanic areas like Iceland, Mexico, and the Western United States (Oregon/California).

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Blue Apatite

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