sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, brown, olive green; Luster: Waxy to dull; Crystal structure: Microcrystalline (Trigonal/Hexagonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Hardness: 6
Color: Tan, brown, olive green
Luster: Waxy to dull

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, olive green; Luster: Waxy to dull; Crystal structure: Microcrystalline (Trigonal/Hexagonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or groundwater environments; typically found as nodules or bedded deposits within limestone or sandstone.

Uses & applications

Historically used for stone tools/arrowheads; currently used in jewelry (as a lapidary material for tumbling), construction aggregate, and as a collector's specimen.

Geological facts

Chert is so durable that it often survives long after the surrounding rock has eroded away. It was one of the most important minerals for early humans due to its ability to break into razor-sharp edges.

Field identification & locations

Identify by its waxy luster, smooth conchoidal fracture (curved like glass), and inability to be scratched by a steel nail. Commonly found in riverbeds or coastal areas.