sedimentary

Banded Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Multi-colored bands (dark grey, white, tan); Luster: Waxy to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Multi-colored bands (dark grey, white, tan)
Luster: Waxy to dull

Identified June 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of siliceous remains of microscopic organisms (like diatoms/radiolarians) in deep-sea environments or via chemical precipitation. The bands represent changes in impurity levels and oxygenation during sedimentation.

Uses & applications

Historically used for making stone tools due to sharp edges; currently used for decorative purposes, landscape gravel, jewelry tumbling, and as a collective river stone.

Geological facts

This specific piece is a water-worn beach or river pebble showing distinct contact between different sedimentary layers. Chert is so hard it can create sparks when struck against steel, a property similar to flint.

Field identification & locations

Identify by its waxy appearance, smooth feel from water erosion, and inability to be scratched by a steel knife. Commonly found in riverbeds, glacial deposits, and coastal beaches.