igneous
Obsidian Arrowhead
Volcanic Glass (predominantly SiO2)
Hardness: 5-6 (Mohs); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.35-2.6
- Hardness
- 5-6 (Mohs)
- Color
- Jet black
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-6 (Mohs); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal fracture; Specific Gravity: 2.35-2.6
Formation & geological history
Formed through the rapid cooling of felsic lava, preventing crystal growth. Most obsidian is geologically young, typically younger than Cretaceous as it devitrifies over time.
Uses & applications
Historically used for weapons and tools; currently used for surgical scalpel blades, jewelry, and as a decorative/collectible artifact.
Geological facts
Obsidian fractures with extremely sharp edges, leading to its historic use as weaponry. This specimen is an arrowhead, a human-modified lithic artifact.
Field identification & locations
Identify by its glass-like appearance, razor-sharp edges, and curved (conchoidal) fracture patterns. Found in volcanic regions like Oregon, California, Iceland, and Mexico.
