sedimentary
Chert (Arrowhead or Projectile Point)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Dark grey to charcoal (likely due to carbonaceous material); Luster: Dull to waxy; Structure: Microcrystalline with no visible grains; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Dark grey to charcoal (likely due to carbonaceous material)
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Dark grey to charcoal (likely due to carbonaceous material); Luster: Dull to waxy; Structure: Microcrystalline with no visible grains; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed in marine environments through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by the replacement of limestone. This specific specimen was later modified by prehistoric humans through knapping. While the rock may be millions of years old, the tool was likely crafted between 1,000 and 10,000 years ago depending on the region found.
Uses & applications
Historically used for manufacture of stone tools, arrowheads, and scrapers due to its sharp conchoidal edges. Currently valued as archaeological artifacts for research and private collection.
Geological facts
Chert and its variant, flint, were the essential 'technology' of the Stone Age. Because it breaks into predictable, razor-sharp edges, it was the primary material for survival tools for millennia.
Field identification & locations
Identify in the field by looking for 'flake' scars (conchoidal ripples) and a sharp, worked edge that distinguishes it from naturally weathered rock. Frequently found in riverbeds or tilled fields near ancient water sources. If found in situ, it may represent a significant archaeological site.
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