sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)

Hardness: 6
Color: reddish-brown
Luster: waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)

Formation & geological history

Formed from the accumulation of silica-rich microfossils or via chemical precipitation within sedimentary rock layers, often associated with iron oxide impurities which give it the dark brown color.

Uses & applications

Historical use for stone tools/arrowheads due to its sharp edges; modern use as gemstones, landscaping rock, and in jewelry (lapidary).

Geological facts

Chert is so durable that it is often found in riverbeds long after the surrounding rock has weathered away. It was a primary material used by prehistoric humans for creating flint tools.

Field identification & locations

Identify by its hardness (will scratch glass) and its smooth, curved conchoidal fractures. Common in limestone formations and gravel deposits worldwide.