sedimentary

Flint

SiO2 (Microcrystalline Quartz)

Hardness of 7 on the Mohs scale, typically dark gray or brown, waxy to vitreous luster, and exhibits distinct conchoidal fracture.

Identified October 17, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, typically dark gray or brown, waxy to vitreous luster, and exhibits distinct conchoidal fracture.

Formed through the replacement of calcium carbonate by silica-rich solutions in chalk or limestone formations during the Cretaceous period.

Historically used for making stone tools and fire-starting; currently utilized in abrasive grit and occasionally for decorative landscaping.

Flint played a crucial role in human technological development during the Stone Age due to its ability to be chipped into extremely sharp edges.

Easily identified by its sharp conchoidal fracture and hardness that can scratch glass. Commonly found in chalk deposits 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

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)