sedimentary

Green Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Olive green to moss green; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Microcrystalline); Cleavage: None (has conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Olive green to moss green
Luster: Waxy to vitreous

Identified May 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or chemical precipitation from hydrothermal fluids in marine environments. This specimen shows a waxy luster and conchoidal fractures typical of chert/jasper varieties.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges; modernly used as a lapidary material, in jewelry, and for ornamental stone collection.

Geological facts

Green chert is sometimes called 'Green Jasper' or 'Prase'. Because of its extreme hardness and the way it breaks into razor-sharp edges, it was a primary material for prehistoric arrowheads and scrapers.

Field identification & locations

Identify in the field by its waxy appearance, sharp curved (conchoidal) edges when broken, and it should be hard enough to scratch glass. Commonly found in stream beds, gravel deposits, and sedimentary limestone formations globally.