sedimentary

Chert (Jasper)

Silicon dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brownish-yellow, tan, or ochre; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Brownish-yellow, tan, or ochre
Luster: Dull to waxy

Identified May 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brownish-yellow, tan, or ochre; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments; common in Paleozoic to Cenozoic strata.

Uses & applications

Used historically for stone tools and arrowheads; today used for decorative gravel, jewelry (cabochons), and as a landscape stone.

Geological facts

This variety of chert is often called Jasper when it is opaque and colored by iron oxides. It breaks with a sharp edge, making it a primary material for prehistoric lithic technology.

Field identification & locations

Identify by its waxy luster on fresh surfaces, extreme hardness (scratches glass), and characteristic curved conchoidal fractures. Commonly found in stream beds or limestone outcrops.