sedimentary
Chert (Flint / Chalcedony pebble)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectMohs hardness 6.5–7, waxy to dull luster, conchoidal fracture, and a mottled tan, brown, and cream coloration.
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Physical properties
Mohs hardness 6.5–7, waxy to dull luster, conchoidal fracture, and a mottled tan, brown, and cream coloration.
Formation & geological history
Formed via biochemical precipitation or silica replacement of carbonate sediments in shallow marine environments during various geological eras.
Uses & applications
Historically used for knapped stone tools and fire-striking; modern uses include construction aggregate and decorative gravel.
Geological facts
Chert produces hot sparks when struck against iron or steel, a property utilized by prehistoric humans to ignite tinder.
Field identification & locations
Identifiable by its smooth, curved conchoidal fractures, microcrystalline texture, and ability to easily scratch glass. Found widely in river gravels, limestone beds, and coastal deposits.
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