sedimentary

Banded Chert

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Greyish-green with brown/red bands; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Greyish-green with brown/red bands
Luster: Waxy to dull

Identified July 21, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Greyish-green with brown/red bands; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. The ribbons or bands indicate seasonal or tidal changes during deposition.

Uses & applications

Historically used for stone tools/weapons; currently used for lapidary work, tumbling, and as an architectural aggregate.

Geological facts

Chert has been used by humans for hundreds of thousands of years to create sparks and sharp-edged tools due to its incredible hardness and predictable fracture patterns.

Field identification & locations

Identify in the field by its waxy texture, inability to be scratched by a steel pocketknife, and sharp, shell-like (conchoidal) edges when broken. Frequently found in riverbeds or limestone outcrops.