sedimentary

Chert

Microcrystalline quartz (SiO2)

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

Identified November 7, 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 tan, brown, or grey.

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

Historically used for making stone tools and arrowheads due to its sharp conchoidal fracture; currently used in abrasives and decorative landscaping.

Chert varieties include flint and jasper. It has been utilized by humans for stone-age weaponry for over two million years.

Identify in the field by its distinct waxy luster, hardness that scratches glass, and sharp, shell-like fracture edges.

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

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)