sedimentary

Flint

Microcrystalline quartz (SiO2)

Hardness: 7 on the Mohs scale. Color: Grey, black, brown, or white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz crystals). Cleavage: None, exhibits characteristic conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Color: Grey, black, brown, or white
Luster: Waxy to vitreous

Identified August 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the diagenesis of siliceous oozes or biochemical deposits containing silica skeletal remains (such as radiolarians or sponge spicules) in marine limestone or chalk formations. Geological age spans from the Mesozoic to Cenozoic eras.

Uses & applications

Historically used for making stone tools, arrowheads, and striking fire. Modern uses include decorative aggregates, abrasive grinding, and historical re-enactment tools.

Geological facts

Flint and chert are essentially the same material, though 'flint' typically refers to the dark nodules found in chalk or marl. Because of its conchoidal fracture, it can be chipped to produce extremely sharp edges, making it one of the most important materials in human prehistory.

Field identification & locations

Can be identified in the field by its smooth, waxy luster, conchoidal fracture surfaces, and occurrence as nodules within limestone or chalk. It easily scratches glass and does not effervesce with dilute hydrochloric acid.