sedimentary

Chert (Jasper-rich)

Silicon Dioxide (SiO2)

Hardness: 7 mohs; Color: Tan, white, and reddish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 mohs
Color: Tan, white, and reddish-brown
Luster: Waxy to dull

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 mohs; Color: Tan, white, and reddish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments and groundwater. Often fills voids in limestone or replaces other minerals.

Uses & applications

Historical use for stone tools and arrowheads; modern use in landscaping, road construction, and as decorative lapidary material for jewelry like cabochons.

Geological facts

Chert was one of the most important minerals for early humans due to its ability to fracture into sharp edges. The reddish variety is often specifically called jasper.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and the way it breaks into smooth, curved 'shell-like' surfaces. Found globally in sedimentary rock outcrops.