sedimentary

Chert (Jasper/Flint variety)

Sedimentary silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: Brown, tan, and reddish-orange. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 7 on Mohs scale
Color: Brown, tan, and reddish-orange
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Brown, tan, and reddish-orange. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Formation & geological history

Formed from the accumulation of silica-rich microfossils or through chemical precipitation from groundwaters in sedimentary environments such as limestone or shale beds.

Uses & applications

Historically used for stone tools and sparks; currently used in landscaping and as a collector specimen. Semi-precious varieties are used in jewelry.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture allows it to be shaped into razor-sharp tools like arrowheads and knives.

Field identification & locations

Identify in the field by its hardness (will scratch glass), waxy luster on fresh surfaces, and smooth, curved fracture edges. Commonly found in riverbeds and limestone outcrops.