sedimentary

Chert Nodule

Cryptocrystalline quartz (SiO2)

Hardness 7 on Mohs scale, dull to waxy luster, conchoidal fracture, various dark or earthy colors.

Identified November 15, 2026More sedimentary →

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Physical properties

Hardness 7 on Mohs scale, dull to waxy luster, conchoidal fracture, various dark or earthy colors.

Formed by the chemical precipitation of silica in marine environments over millions of years.

Historically used by early humans for making stone tools; occasionally used for decorative landscaping or lapidary work.

Chert often forms nodules within limestone or chalk formations and creates extremely sharp edges when fractured.

Identify by its conchoidal fracture and high hardness that scratches glass easily; found globally in limestone regions.

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