sedimentary

Flint

Sedimentary cryptocrystalline quartz (SiO2)

Hardness of 7 on the Mohs scale, typically dark grey, brown, or black, with a waxy to vitreous luster and conchoidal fracture.

Identified November 14, 2026More sedimentary →

Get a report just like this from any photo, free.

Physical properties

Hardness of 7 on the Mohs scale, typically dark grey, brown, or black, with a waxy to vitreous luster and conchoidal fracture.

Formed through the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions over millions of years.

Historically used for making stone tools and fire-striking implements, and presently collected as a geological specimen.

Flint and chert are essentially the same material, though flint typically forms as nodules in chalk formations.

Identified easily by its distinctive conchoidal fracture and sharp edges, commonly found embedded in chalk cliffs 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