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

Identified May 29, 2026More igneous →

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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.

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