sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, typically gray-green or brown in color, waxy to vitreous luster, and exhibits conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, typically gray-green or brown in color, waxy to vitreous luster, and exhibits conchoidal fracture.
Formation & geological history
Formed through the chemical precipitation of silica from seawater or the replacement of limestone by silica-rich solutions over millions of years.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-striking implements due to its sharp edges when fractured.
Geological facts
Chert is extremely durable and resistant to weathering, often outlasting the host limestone in which it forms.
Field identification & locations
Identify it in the field by its smooth, rounded weathered exterior, conchoidal fracture, and ability to scratch glass easily.
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