sedimentary

Chert Nodule

Microcrystalline Quartz (SiO2)

Hardness of 7 on Mohs scale, waxy luster, conchoidal fracture, and typically white, grey, or brown coloration.

Identified November 13, 2026More sedimentary →

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Physical properties

Hardness of 7 on Mohs scale, waxy luster, conchoidal fracture, and typically white, grey, or brown coloration.

Formed via the replacement of calcium carbonate by silica-rich solutions within marine limestone or chalk deposits.

Historically used by early humans for making stone tools and arrowheads due to its sharp fracture edges.

Chert nodules often weather out of softer limestone matrices, leaving rugged, knobby shapes resistant to erosion.

Identify by its extreme hardness, conchoidal fracture pattern, and waxy appearance. Commonly found globally in sedimentary rock formations.

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