igneous

Obsidian

Obsidian (Volcanic Glass, SiO2 dominated)

Hardness: 5.0–6.0; Color: Black, dark brown, or grey; Luster: Vitreous (glassy); Crystal Structure: Amorphous; Cleavage: None (conchoidal fracture); Specific Gravity: 2.35–2.6; Features: Sharp edges and smooth, curved surfaces when broken.

Hardness: 5
Color: Black, dark brown, or grey
Luster: Vitreous (glassy)

Identified May 10, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of silica-rich felsic lava, which prevents crystal growth. It is found in geologically recent volcanic fields or areas with rhyolitic activity.

Uses & applications

Historically used for arrowheads and blades; currently used for surgical scalpels, decorative gemstones, jewelry, and metaphysical collecting.

Geological facts

Obsidian is technically a glass rather than a true mineral because it lacks a crystalline structure. Native American tribes traded obsidian across vast distances for tool making.

Field identification & locations

Identify in the field by its distinctive glassy appearance and conchoidal (shell-like) fracture patterns. Commonly found in Oregon, California, Iceland, and Mexico. Collectors look for unique variations like snowflake, mahogany, or rainbow obsidian.

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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