sedimentary
Chert (often called Flint)
Chert (Microcrystalline Quartz, SiO2)
Hardness: 6.5-7 on Mohs scale; Color: typically grey, brown, or tan; Luster: dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: none.
- Hardness
- 6
- Color
- typically grey, brown, or tan
- Luster
- dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: typically grey, brown, or tan; Luster: dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: none.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the chemical replacement of limestone/dolomite by silica-rich fluids. Generally dates from various periods throughout the Phanerozoic eon.
Uses & applications
Historically used for stone tools (knives, scrapers, arrowheads) due to its sharp edges. Today used in construction aggregate, road surfacing, and as a sparking element in survival gear.
Geological facts
This specimen appears to be an anthropogenic lithic flake or core, meaning it was shaped by ancient humans. Its sharply defined ridges (arrises) are characteristic of prehistoric tool-making techniques.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), waxy feel, and unique conchoidal fracture scars. Found commonly in limestone beds or as nodules in chalk.
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