sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Yellowish-brown to tan with dark inclusions; Luster: Dull to waxy; Crystal Structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Yellowish-brown to tan with dark inclusions
Luster: Dull to waxy

Identified June 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary environments. Can be found in geological formations ranging from the Precambrian to recent ages.

Uses & applications

Used primarily as lapidary material for jewelry, cabochons, and decorative items. Historically significant for making stone tools (lithics) like scrapers and arrowheads due to its sharp edges when fractured.

Geological facts

Jasper is an opaque variety of chalcedony. The yellow-brown color in this specimen is typically caused by the presence of iron oxide (goethite). It is one of the most common materials used by early humans for tool-making.

Field identification & locations

Identify in the field by its waxy texture and characteristic conchoidal (shell-like) fracture patterns. It will scratch glass but cannot be scratched by a steel knife. Commonly found in riverbeds, desert pavements, and as nodules within limestone or chalk.