Black obsidian cabochon or sphere

Very dark black, vitreous glassy luster, smooth polished surface, and no visible crystal structure or cleavage. Hardness is about 5–5.5 Mohs; conchoidal fracture and typical specific gravity is 2.35–2.65.

Obsidian forms when silica-rich lava cools so rapidly that crystals cannot grow, generally in volcanic flows and domes during the Quaternary and older volcanic periods. This specimen has been human-shaped and highly polished.

Used for ornamental spheres, cabochons, carvings, jewelry, and historical blades; it is valued mainly as a decorative lapidary material rather than a construction stone.

Its apparent blackness comes from glassy iron-bearing melt; thin edges may appear brown, gray, or translucent. Tiny round marks visible in the image may be polishing pits, bubbles, or surface inclusions.

Identify by its uniform glassy appearance, sharp conchoidal fracture when unpolished, lack of grains, and absence of cleavage; volcanic obsidian is common in Mexico, the western United States, Armenia, Turkey, and Japan. A glass imitation may be distinguished by testing provenance, density, and fracture behavior.