sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Mohs hardness: 7. Color: Tan, brown, and grey with possible banding. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 7
- Color
- Tan, brown, and grey with possible banding
- Luster
- Waxy to dull
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Physical properties
Mohs hardness: 7. Color: Tan, brown, and grey with possible banding. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed by the accumulation of siliceous remains of organisms (radiolarians, diatoms) or chemical precipitation of silica in marine or groundwater environments. Found in Paleozoic to Cenozoic limestone and chalk deposits.
Uses & applications
Historically used for stone tools and fire-starting. Currently used as a road aggregate, in jewelry (as jasper/agate varieties), and for flintknapping hobbyists.
Geological facts
Flint is a variety of chert that was essential for early human survival in making arrowheads and knives. It produces sparks when struck against steel.
Field identification & locations
Identify by its smooth, waxy surface and sharp, curved conchoidal fractures. Commonly found in stream beds or weathered out of limestone cliffs.
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