sedimentary

Chert (Jasper/Flint var.)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Brownish-red to tan due to iron oxides; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 Mohs scale
Color: Brownish-red to tan due to iron oxides
Luster: Waxy to dull

Identified June 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation from silica-rich fluids in limestone or chalk beds. Often Cretaceous to Paleozoic in age.

Uses & applications

Historically used for stone tools (knapping) due to sharp edges; currently used for road surfacing, jewelry (as Jasper), and landscaping.

Geological facts

Chert is so hard it can strike sparks against steel, which made it the primary material for flintlock firearms and ancient fire-starting kits.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and inability to be scratched by a steel knife. Commonly found in riverbeds or as nodules within limestone outcrops.