sedimentary
Chert
Microcrystalline Quartz (SiO2)
Mohs hardness of 7, dull to waxy luster, microcrystalline/cryptocrystalline texture, conchoidal fracture, grayish-brown to tan coloration with mottling.
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Physical properties
Mohs hardness of 7, dull to waxy luster, microcrystalline/cryptocrystalline texture, conchoidal fracture, grayish-brown to tan coloration with mottling.
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of siliceous organism remains (such as radiolarians or diatoms) in marine or lacustrine environments.
Uses & applications
Historically used by ancient cultures to fashion sharp edged tools and arrowheads. Currently used in road construction material, aggregate, and as minor decorative rock.
Geological facts
Chert is famous for its ability to produce sharp edges when struck, making it a primary material for prehistoric tools and weapons alongside flint.
Field identification & locations
Identified by its high hardness (scratches steel), smooth waxy feel, conchoidal fracture pattern, and lack of visible grains. Found globally in sedimentary limestone or chalk beds.
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