sedimentary

Banded Chert

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Tan, brown, and cream bands; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 7 Mohs scale
Color: Tan, brown, and cream bands
Luster: Waxy to dull

Identified July 5, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Tan, brown, and cream bands; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Forms through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments, dating from the Precambrian to recent periods.

Uses & applications

Used historically for stone tools due to its sharp edges when broken; currently used as aquarium gravel, decorative landscaping stones, and occasionally for lapidary art.

Geological facts

Chert is essentially a non-gemstone variety of jasper or agate. It is incredibly durable and resistant to chemical weathering.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel nail) and the presence of shell-like (conchoidal) fracture lines. Found globally in limestone and chalk beds.