sedimentary

Chert (Nodule)

Chert (composed of Microcrystalline Silica/SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and grey, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Hardness: 6

Identified April 11, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and grey, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the precipitation of silica from groundwater filling voids in limestone or chalk beds, or from the accumulation of siliceous skeletal remains of marine organisms. Primarily found in Phanerozoic sedimentary sequences.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers); currently used in road construction, as decorative stone, and occasionally in jewelry as jasper/agate variants.

Geological facts

Chert was one of the most important minerals for early humans due to its ability to produce sharp edges when fractured. Variations include flint, jasper, and chalcedony.

Field identification & locations

Identify in the field by its hardness (wont be scratched by steel) and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in limestone outcrops or as rounded pebbles in riverbeds.