sedimentary

Banded Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Grey, black, and white banding; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Grey, black, and white banding
Luster: Waxy to vitreous

Identified July 3, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Grey, black, and white banding; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. Banding occurs due to seasonal or chemical fluctuations during deposition. Common in Paleozoic and Mesozoic strata.

Uses & applications

Historically used for making sharp tools and weapons (arrowheads). Modernly used as tumbles, decorative stones, and aggregate in construction.

Geological facts

Chert is essentially the same material as flint, but the term chert is generally used for lighter colored or non-chalk-associated varieties. It can occasionally contain microscopic fossils like radiolarians.

Field identification & locations

Identified by its extreme hardness (scratches glass), waxy luster when polished, and distinctive curved (conchoidal) fractures. Found in riverbeds and limestone outcrops globally.