sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Reddish-brown, tan, pink (due to iron oxides); Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, tan, pink (due to iron oxides)
Luster: Waxy to dull

Identified March 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation from hydrothermal fluids in sedimentary environments. Common in Precambrian to Cenozoic formations.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in lapidary work for cabochons and jewelry, as well as industrial abrasives and decorative landscaping stone.

Geological facts

Jasper is an opaque variety of chert. Because it fractures into sharp edges, it was one of the most important minerals for early humans to create survival tools. The color is often mottled or banded due to varying mineral impurities.

Field identification & locations

Identify by its 'shell-like' conchoidal fracture patterns and the fact that it will easily scratch glass. Commonly found in stream beds or within limestone and dolomite formations. Collectors should look for unique patterns or bright red colors.