sedimentary

Flint

Microcrystalline quartz (SiO2)

Hardness of 7 on Mohs scale, waxy luster, conchoidal fracture, and typically brown, grey, or tan in color.

Identified November 15, 2026More sedimentary →

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Physical properties

Hardness of 7 on Mohs scale, waxy luster, conchoidal fracture, and typically brown, grey, or tan in color.

Formed through the chemical replacement of limestone or chalk by silica-rich groundwater during the Cretaceous period.

Historically used for making stone tools, arrowheads, and striking fire; currently collected for lapidary and historical interest.

Flint is extremely durable and breaks with razor-sharp edges, making it the premier material for ancient stone technology.

Identified by its distinct conchoidal fracture and waxy appearance, commonly found nodules embedded within chalk or limestone 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