sedimentary
Chert (Arrowhead/Tool variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Brownish-red to tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater. This specimen appears to have been culturally modified (knapped) into a tool.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers, knives) due to its sharp conchoidal fracture. Modern use includes historical collection and study of lithic technology.
Geological facts
Chert was one of the most vital materials for early humans; it produces edges sharper than steel scalpels when freshly fractured. This specific piece shows signs of human alteration.
Field identification & locations
Identify by its waxy appearance, extreme hardness (it will scratch glass), and the 'scalloped' flake scars typical of conchoidal fracturing. Often found in limestone or chalk beds.
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