igneous
Obsidian arrowhead
Volcanic glass (predominantly rhyolitic SiO₂)
AI-generated identification · may be incorrectHardness ~5–5.5 Mohs; black to blue-black, vitreous luster, amorphous/noncrystalline structure, and excellent conchoidal fracture producing razor-sharp edges. The symmetrical flaking and shape indicate human knapping rather than a natural fragment.
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Physical properties
Hardness ~5–5.5 Mohs; black to blue-black, vitreous luster, amorphous/noncrystalline structure, and excellent conchoidal fracture producing razor-sharp edges. The symmetrical flaking and shape indicate human knapping rather than a natural fragment.
Formation & geological history
Obsidian forms when silica-rich lava cools rapidly, typically during volcanic eruptions; individual deposits range from Quaternary to much older volcanic ages. This piece was shaped into a projectile point by controlled pressure or percussion flaking.
Uses & applications
Historically used for cutting tools, knives, spear and arrow points, and ritual objects; today it is primarily collectible or decorative. It is not generally used as a structural construction stone.
Geological facts
Obsidian lacks true crystals and can show flow banding or tiny gas bubbles; its sharp fracture supported sophisticated prehistoric toolmaking. Blue sheen may reflect surface reflections, hydration, or subtle inclusions rather than blue mineral crystals.
Field identification & locations
Identify by its glassy luster, curved conchoidal scars, sharp edges, and absence of granular crystals; check for uniform flake scars and intentional symmetry. Common sources include Arizona, New Mexico, Oregon, California, Mexico, Armenia, and the Near East.
