sedimentary

Chert (Red/Pink Jasper subtype)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Reddish-pink to tan; Luster: Dull/Waxy; Crystal Structure: Cryptocrystalline (microscopic quartz crystals); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Reddish-pink to tan
Luster: Dull/Waxy

Identified March 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. Often found as nodules in limestone or beds within sedimentary sequences. Geological age varies widely from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads/knives) due to sharp edges; currently used for decorative stones, landscaping, and jewelry (as jasper).

Geological facts

Because of its extreme hardness and ability to break into razor-sharp edges, chert was the primary 'high-tech' material for prehistoric humans across the globe for thousands of years.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its conchoidal (shell-like) fracture pattern. Commonly found in riverbeds or eroded out of limestone cliffs. Collectors should look for unique color swirling or 'patterned jasper' varieties.

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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