sedimentary
Chert (Arrowhead Fragment)
Cryptocrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, brown to grey color, cryptocrystalline crystal structure.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, brown to grey color, cryptocrystalline crystal structure.
Formation & geological history
Formed through the chemical precipitation of silica in marine environments or the replacement of limestone by silica-rich solutions over millions of years during the Paleozoic era and later.
Uses & applications
Historically used by indigenous peoples for making sharp tools and weapons such as arrowheads and scrapers; currently of interest to artifact collectors and geologists.
Geological facts
Chert breaks with a sharp conchoidal fracture, making it an ideal material for knapping into primitive stone tools.
Field identification & locations
Found worldwide in sedimentary rock formations, particularly within chalk and limestone deposits. Identified by its hardness, conchoidal fracture, and waxy luster.
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