sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, typically grey, white, brown, or black in color, waxy to vitreous luster, cryptocrystalline structure with conchoidal fracture, and specific gravity around 2.6.
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Physical properties
Hardness of 7 on the Mohs scale, typically grey, white, brown, or black in color, waxy to vitreous luster, cryptocrystalline structure with conchoidal fracture, and specific gravity around 2.6.
Formation & geological history
Formed by the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of marine organisms such as radiolarians and diatoms, typically during the Mesozoic and Paleozoic eras.
Uses & applications
Historically used by early humans for making stone tools such as arrowheads and knives due to its conchoidal fracture. Today used in abrasives and occasionally decorative landscaping.
Geological facts
Chert is extremely durable and resistant to weathering, which is why ancient stone tools made from chert survive intact for thousands of years. Varieties include flint and jasper.
Field identification & locations
Can be identified in the field by its sharp conchoidal fracture edges and hardness that easily scratches glass. Commonly found within limestone and chalk formations worldwide.
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