sedimentary

Green Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on Mohs scale; Color: olive green to brownish; Luster: waxy to vitreous; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.6–2.7.

Hardness: 6
Color: olive green to brownish
Luster: waxy to vitreous

Identified March 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. It often occurs as nodules or layers within limestone or shale.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges; modernly used in landscaping, as aquarium stones, or tumbled for jewelry and lapidary art.

Geological facts

Chert is so durable that it often survives millions of years of erosion, frequently appearing as smooth river stones. Green varieties specifically often get their color from chlorite or iron inclusions.

Field identification & locations

Identify in the field by its smooth, waxy texture and shell-like (conchoidal) fractures. It will scratch glass but cannot be scratched by a steel knife. Commonly found in riverbeds and coastal regions.