sedimentary
Chert (Arrowhead Fragment)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: black to dark grey with brown weathering rind (cortex); Luster: vitreous to waxy; Structure: microcrystalline quartz; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- black to dark grey with brown weathering rind (cortex)
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: black to dark grey with brown weathering rind (cortex); Luster: vitreous to waxy; Structure: microcrystalline quartz; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed as nodules or layered deposits in sedimentary rocks (typically limestone or chalk) through the precipitation of silica. This specific piece shows evidence of anthropogenic flaking.
Uses & applications
Historically used for tools (knapping) such as arrowheads, scrapers, and knives due to its sharp edges. Modern uses include abrasive tools and geological study.
Geological facts
This specimen appears to be a lithic flake or fragment of a projectile point. Chert has been used by humans for hundreds of thousands of years because it fractures predictably to create razor-sharp edges.
Field identification & locations
Identified by its waxy luster, conchoidal (shell-like) fracture patterns, and hardness. If found in a suspected archaeological context, it should be reported to local authorities.
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