sedimentary
Chert (Flint nodule)
Chert (SiO2)
Hardness: 7 (Mohs), Color: Grey, Tan, White, Luster: Waxy to dull, Structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs), Color: Grey, Tan, White, Luster: Waxy to dull, Structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments like limestone or chalk beds.
Uses & applications
Historical use for stone tools (arrowheads), modern use in construction aggregate, and occasionally for lapidary work.
Geological facts
Flint is a variety of chert. When struck against steel, flint can produce sparks, which made it vital for starting fires and for use in early firearms.
Field identification & locations
Look for a smooth, waxy surface where freshly broken and a sharp, glass-like edge. Commonly found as nodules within limestone or chalk deposits.
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