sedimentary

Chert (Banded)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, brown with banded layers, Luster: waxy to dull, Structure: cryptocrystalline, Fracture: conchoidal

Hardness: 6

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, brown with banded layers, Luster: waxy to dull, Structure: cryptocrystalline, Fracture: conchoidal

Formation & geological history

Formed by the accumulation of siliceous remains of organisms (radiolarians/diatoms) or chemical precipitation from silica-rich groundwater within limestone or chalk beds.

Uses & applications

Used historically for stone tools and arrowheads; currently used as road aggregate, in jewelry as semi-precious stones, and as a decorative landscaping rock.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges.

Field identification & locations

Identify by its hardness (cannot be scratched by a knife), waxy appearance, and layered or banded patterns. Commonly found in riverbeds, gravel pits, and sedimentary outcrops.