sedimentary

Chert (Jasper-rich)

Microcrystalline/Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, brown, and reddish-orange due to iron oxides; Luster: Dull to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Tan, brown, and reddish-orange due to iron oxides
Luster: Dull to waxy

Identified May 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation from silica-rich fluids in sedimentary basins. This specimen likely dates from the Paleozoic or Mesozoic eras and developed in marine or volcanic environments.

Uses & applications

Historically used for stone tools and arrowheads due to its sharp conchoidal fracture. Currently used in road construction as aggregate and occasionally as ornamental stones or for lapidary work if highly colored.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most vital materials for prehistoric humans to create cutting tools and fire-starting kits.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. Commonly found in limestone or dolomite beds as nodules or layers.

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