igneous
Obsidian (likely Apache tear or flaked obsidian)
Volcanic glass; primarily rhyolitic silica glass (SiO₂-rich, non-crystalline)
AI-generated identification · may be incorrectTypically black, vitreous to resinous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5; the specimen shows sharp flake-like fractures and reflective surfaces. Its irregular, glossy texture is consistent with worked or naturally fractured obsidian.
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Physical properties
Typically black, vitreous to resinous luster, conchoidal fracture, no cleavage, and Mohs hardness about 5–5.5; the specimen shows sharp flake-like fractures and reflective surfaces. Its irregular, glossy texture is consistent with worked or naturally fractured obsidian.
Formation & geological history
Forms when silica-rich lava cools so rapidly that crystals cannot grow, commonly during Quaternary volcanic eruptions. Major sources include Mexico, the western United States, Iceland, Armenia, and the Mediterranean.
Uses & applications
Historically knapped into exceptionally sharp blades, spear points, and tools; today used for ornaments, cabochons, carving, and geological collections. It has modest value unless unusually transparent, patterned, or historically significant.
Geological facts
Obsidian is technically a mineraloid rather than a true mineral because it lacks a crystal lattice. Thin edges can be sharper than surgical steel, though they are brittle and easily chipped.
Field identification & locations
Identify by its glassy black appearance, very sharp conchoidal edges, lack of visible grains, and inability to scratch ordinary glass reliably. The pictured piece may be a knapped artifact, but confirmation requires archaeological context and edge analysis.
