sedimentary

Banded Chert

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs), Color: Gray and yellow/gold banding, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal

Hardness: 6

Identified June 13, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs), Color: Gray and yellow/gold banding, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine environments; the layering reflects seasonal or geological changes in water chemistry.

Uses & applications

Primarily used as decorative display pieces, in lapidary work for cabochons, and historically for stone tools due to its sharp edges.

Geological facts

Chert is a chemical sedimentary rock that can contain microscopic biological remains. It is extremely durable and chemically stable, often remaining intact while surrounding limestone erodes away.

Field identification & locations

Look for distinctive color banding and a smooth, waxy texture. It is harder than steel and will scratch glass. Commonly found in riverbeds and coastal regions as water-tumbled pebbles.