sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs. Color: Tan, yellow-brown, or ochre. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Hardness: 6
Color: Tan, yellow-brown, or ochre
Luster: Dull to waxy

Identified March 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs. Color: Tan, yellow-brown, or ochre. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from hydrothermal fluids. This specimen appears water-worn, likely from an alluvial or glacial deposit.

Uses & applications

Historically used for stone tools and fire-starting (flint). Currently used as decorative landscaping rock, jewelry (when polished as jasper), and as a gemstone for collectors or 'pocket stones'.

Geological facts

Chert breaks with a conchoidal fracture, creating razor-sharp edges which made it the primary material for arrowheads and spear points in the Stone Age. It is chemically identical to quartz but has a much finer grain.

Field identification & locations

Identify in the field by its wax-like texture, smoothness, and 'clinking' sound when struck with metal. It cannot be scratched by a steel knife. Common in limestone regions and creek beds globally.