sedimentary
Chert
Microcrystalline quartz (SiO2)
Hardness of 7 on the Mohs scale, colors range from white, grey, brown to reddish-brown, waxy to vitreous luster, conchoidal fracture, crypto-crystalline structure, specific gravity around 2.60-2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors range from white, grey, brown to reddish-brown, waxy to vitreous luster, conchoidal fracture, crypto-crystalline structure, specific gravity around 2.60-2.65.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions, often accumulating from the skeletal remains of microscopic marine organisms like radiolaria and diatoms, or replacement of limestone.
Uses & applications
Historically used by ancient humans for making stone tools such as arrowheads, spear points, and blades due to its sharp conchoidal fracture. Also used historically for striking fire.
Geological facts
Chert varieties include flint, jasper, and chalcedony. Because of its durability and fine grain, chert artifacts are among the most common and well-preserved archaeological finds globally.
Field identification & locations
Identified easily by its hardness (scratches glass), waxy luster, and distinctive conchoidal (shell-like) fracture. Commonly found in limestone and chalk formations worldwide.
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