igneous
Obsidian / Chert (Arrowhead Artifact)
Obsidian (volcanic glass, SiO2 with impurities)
Hardness: 5-5.5 Mohs; Color: Black to dark grey; Luster: Vitreous/glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 5-5
- Color
- Black to dark grey
- Luster
- Vitreous/glassy
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Physical properties
Hardness: 5-5.5 Mohs; Color: Black to dark grey; Luster: Vitreous/glassy; Structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the rapid cooling of silica-rich lava which prevents crystal growth. This specific artifact dates to the Paleo-Indian/Early Archaic period (approx. 8,500 - 7,550 years Before Present).
Uses & applications
Archaeological artifact used as a projectile point/spear head; historically used for cutting tools and modernly for high-end scalpel blades and jewelry.
Geological facts
This specimen is an 'Angostura' style projectile point, part of the Plano tradition in the High Plains of North America. It signifies highly skilled percussion and pressure flaking techniques.
Field identification & locations
Identify by the lanceolate shape, concave base, and oblique flaking patterns. Commonly found in North American Great Plains sites. Note: It is often illegal to remove such items from public or tribal lands.
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