sedimentary

Chert

Microcrystalline quartz (SiO2)

Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and colors ranging from white to gray, brown, or black.

Identified November 14, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and colors ranging from white to gray, brown, or black.

Formed through the chemical precipitation of silica from seawater or the replacement of limestone by silica-rich solutions over millions of years.

Historically used by ancient humans for making stone tools, arrowheads, and blades due to its sharp conchoidal fracture.

Chert that is dark or black in color is frequently referred to as flint. It is extremely durable and resistant to weathering.

Identify in the field by its hard conchoidal edges and waxy appearance. Commonly found within sedimentary limestone and chalk deposits worldwide.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Shale

Fissile Sedimentary Rock

Sandstone

Arenite

Shale

Clastic sedimentary rock