sedimentary

Green Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Dark green to olive; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/cryptocrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Dark green to olive
Luster: Waxy to vitreous

Identified January 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in marine environments. This specimen appears consistent with formations ranging from the Paleozoic to Mesozoic eras.

Uses & applications

Used historically for stone tools and arrowheads due to its sharp edges when fractured. Modern uses include jewelry (cabochons), landscaping, and as an industrial abrasive.

Geological facts

Chert is so tough and chemically stable that it is often found as smooth pebbles in riverbeds or beaches long after the surrounding rock has eroded away. Green varieties are specifically often called 'Green Jasper' in the gemstone trade.

Field identification & locations

Identify in the field by its distinct conchoidal (shell-like) fracture pattern and its ability to scratch glass. It is commonly found in sedimentary basins, particularly within limestone or shale beds, and in many coastal areas as water-worn cobbles.