sedimentary

Banded Chert

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, brown, and purple bands; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Tan, brown, and purple bands
Luster: Dull to waxy

Identified July 16, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, and purple bands; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, with banding caused by fluctuating iron oxides or clay content.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges when fractured; today used for lapidary work and as a collector's specimen.

Geological facts

Chert is chemically very similar to flint and jasper; the distinctive banding in this specimen is likely due to rhythmic sedimentation or seasonal changes during formation.

Field identification & locations

Look for microcrystalline texture that cannot be scratched by a steel nail and a shell-like conchoidal fracture pattern. Common in sedimentary basins worldwide.