sedimentary

Banded Chert

Silicon Dioxide (SiO2) with impurities

AI-generated identification · may be incorrect

Hardness: 6.5-7; Color: Yellow, tan, and brown with dark purple/grey mineral bands; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Hardness: 6
Color: Yellow, tan, and brown with dark purple/grey mineral bands
Luster: Waxy to dull

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7; Color: Yellow, tan, and brown with dark purple/grey mineral bands; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often associated with Precambrian formations or secondary replacement in limestone.

Uses & applications

Used historically for stone tools (lithics); currently used in lapidary work, jewelry, and as decorative gravel.

Geological facts

The banding in chert can represent seasonal rhythms in deposition or changes in ocean chemistry; chert is so durable it can survive millions of years of erosion and river transport.

Field identification & locations

Identify by its waxy texture, bands that follow the rock's layering, and its ability to scratch glass. Commonly found in riverbeds and sedimentary basins worldwide.