sedimentary

Banded Flint

Silicon Dioxide (Cryptocrystalline Quartz)

Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct brownish-gray alternating color bands.

Identified November 8, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct brownish-gray alternating color bands.

Formed through the chemical precipitation of silica in marine environments or the replacement of limestone during the Cretaceous period.

Historically used for prehistoric stone tools and fire-starting; currently used in decorative lapidary work and collections.

Flint was crucial for ancient human survival, serving as the primary material for sharp blades, arrowheads, and spark generation.

Identified by its conchoidal fracture, waxy feel, and ability to scratch glass; found globally in chalk and 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

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)