Obsidian

Hardness of 5-5.5 on the Mohs scale, typically dark black or dark brown in color with a vitreous luster, amorphous crystal structure, and exhibits sharp conchoidal fracture.

Formed as an extrusive igneous rock when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.

Historically used for cutting tools, arrowheads, and blades; currently utilized in ornamental jewelry, surgical scalpel blades, and holistic healing.

Despite being considered a rock, obsidian is actually a mineraloid because it lacks a crystalline structure. It cools so quickly that mineral crystals cannot form.

Easily identified by its glass-like appearance, smooth curved conchoidal breakage patterns, and extreme sharpness. Commonly found in regions with recent volcanic activity such as the western United States.