sedimentary
Chert (Nodule)
Chert (composed of Microcrystalline Silica/SiO2)
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
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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.
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