sedimentary
Fossiliferous Chert (Brachiopod/Bryozoan Fossil)
Microcrystalline quartz (SiO2) with fossil inclusions
Hardness of 7 on the Mohs scale, dark gray to black color when wet, vitreous to waxy luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, dark gray to black color when wet, vitreous to waxy luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65.
Formation & geological history
Formed through the replacement of limestone or accumulation of silica-rich skeletal remains in marine environments millions of years ago during the Paleozoic era.
Uses & applications
Used primarily as a geological specimen, lapidary material for cabochons, and for educational study of ancient marine ecosystems.
Geological facts
The intricate mosaic pattern visible on the surface consists of cross-sections of fossilized marine organisms such as bryozoans or brachiopods preserved in silica.
Field identification & locations
Can be identified by its extreme hardness (scratches glass), waxy or glassy luster, and the distinctive micro-fossil patterns visible on polished or wet surfaces. Commonly found in gravel bars and river beds where chert nodules have eroded out of limestone formations.
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