sedimentary

Banded Chert

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Black, blue-grey, tan, and white bands; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 Mohs
Color: Black, blue-grey, tan, and white bands
Luster: Waxy to vitreous

Identified June 28, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Black, blue-grey, tan, and white bands; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in marine environments. Banding represents seasonal or cyclical changes in sediment deposition.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to sharp edges; currently used for jewelry cabochons, lapidary art, and decor.

Geological facts

Banded chert is often associated with some of the oldest known fossils on Earth, such as stromatolites found in Precambrian formations.

Field identification & locations

Identify by its extreme hardness (scratches glass), waxy feel, and smooth curved (conchoidal) fractures. Common in limestone or dolostone beds globally.