sedimentary

Chert

Microcrystalline quartz (SiO2)

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

Identified November 14, 2026More sedimentary →

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Physical properties

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

Formed through the chemical precipitation of silica-rich fluids or accumulation of siliceous microfossil skeletal remains in marine environments.

Historically used for making stone tools, arrowheads, and spark-producing fire starters; presently used in abrasives and road aggregates.

Chert breaks with extremely sharp edges known as conchoidal fractures, making it the preferred material for ancient lithic technology.

Identify by its waxy luster, hardness that scratches glass, and distinct conchoidal fracture patterns found within limestone formations 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