sedimentary

Banded Chert

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Gray, tan, white, and brown bands. Luster: Dull to waxy. Structure: Microcrystalline with conchoidal fracture. Specific gravity: 2.6.

Hardness: 6
Color: Gray, tan, white, and brown bands
Luster: Dull to waxy

Identified July 11, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Gray, tan, white, and brown bands. Luster: Dull to waxy. Structure: Microcrystalline with conchoidal fracture. Specific gravity: 2.6.

Formation & geological history

Formed through the accumulation of silica-rich microfossils or the chemical precipitation of silica in marine or groundwater environments. These specimens can range from Precambrian to Cenozoic in age.

Uses & applications

Historically used for stone tools (knapping) due to its sharp fracture edges. Currently used as road aggregate, in landscaping, and as a collector specimen.

Geological facts

Chert was one of the first materials used by early humans to make arrowheads and scrapers. The banded varieties often form in layers reflecting seasonal or environmental changes during deposition.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its smooth waxy feel, and its shell-like (conchoidal) fracture pattern. Commonly found in limestone or chalk beds.