sedimentary
Chert / Flint
Microcrystalline Quartz (SiO2)
Hardness of 7 on the Mohs scale, typically white, gray, brown, or black in color with a waxy to dull luster. It has a cryptocrystalline structure and exhibits conchoidal fracture with no true cleavage.
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Physical properties
Hardness of 7 on the Mohs scale, typically white, gray, brown, or black in color with a waxy to dull luster. It has a cryptocrystalline structure and exhibits conchoidal fracture with no true cleavage.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions, often replacing carbonate rocks like limestone during diagenesis. Can range in geological age from Precambrian to recent.
Uses & applications
Historically used for making stone tools, arrowheads, and spark generation in firearms. Currently used in road aggregate, abrasives, and sometimes ornamental landscaping.
Geological facts
Chert is extremely durable and weather-resistant, which is why ancient stone tools made from it survive exceptionally well in the archaeological record.
Field identification & locations
Can be identified in the field by its hard, dense nature, smooth conchoidal fracture surfaces, and the fact that it can easily scratch glass. Commonly found within limestone and chalk formations worldwide.
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