sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Tan, brown, or yellowish; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.

Hardness: 6
Color: Tan, brown, or yellowish
Luster: Waxy to dull

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the replacement of limestone. It typically forms in marine sedimentary environments during various geological eras from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in landscaping, as a gemstone (Jasper), and as a component in construction aggregate.

Geological facts

Chert is so hard it can scratch steel and produce sparks when struck against iron; it was one of the primary materials used by prehistoric humans for tool making due to its predictable fracturing pattern.

Field identification & locations

Identify by its 'flint-like' waxy appearance and smooth, shell-like (conchoidal) breaks. This specimen appears as water-worn gravel, commonly found in riverbeds and glacial deposits. For collectors, look for uniform color or interesting patterns.