sedimentary
Blue Chert
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, blueish-grey color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, blueish-grey color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65.
Formation & geological history
Formed by the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of marine organisms diagenetically altered over millions of years.
Uses & applications
Historically used for making stone tools such as arrowheads and spear points due to its conchoidal fracture; occasionally used for decorative carvings or as a collector specimen.
Geological facts
Chert forms in various colors depending on impurities, with blue variations being somewhat less common than grey, brown, or white. It was heavily prized by ancient peoples for knapping into sharp implements.
Field identification & locations
Identified by its hard nature (scratches glass), waxy luster, and sharp conchoidal edges when fractured. Frequently found in limestone formations worldwide.
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