sedimentary

Chert/Flint Nodule

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Variable, often grey, brown, white, or reddish depending on impurities. Luster: Waxy to dull. Crystal structure: Microcrystalline/Cryptocrystalline. Cleavage: None; exhibits conchoidal fracture. Specific gravity: ~2.6.

Hardness: 6
Luster: Waxy to dull

Identified August 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of silica from groundwater or as a biochemical precipitate in marine environments, often replacing carbonate rock or forming nodules in limestone or chalk deposits.

Uses & applications

Historically used for making stone tools and starting fires due to its hardness and conchoidal fracture. Today, it is used occasionally as a semi-precious stone, in landscaping, or as a collector's specimen.

Geological facts

Flint and chert have been crucial to human survival for millennia, providing the sharp edges needed for cutting tools and weapons before the advent of metallurgy.

Field identification & locations

Identified by its hard, smooth surfaces, conchoidal (shell-like) fracture, and waxy luster. Often found in areas with limestone or chalk deposits.

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