sedimentary

Chert / Jasper

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Luster: Waxy to dull; Color: Earthy tones including brown, grey, dark red, and tan; Cleavage: None (conchoidal to irregular fracture); Crystal structure: Trigonal (microcrystalline).

Hardness: 6
Color: Earthy tones including brown, grey, dark red, and tan
Luster: Waxy to dull

Identified July 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine or sedimentary environments through the precipitation of silica-rich fluids or accumulation of siliceous organisms like radiolarians and diatoms, subsequently compacted over geological time.

Uses & applications

Historically used by indigenous peoples for making sharp tools and arrowheads due to its conchoidal fracture. Today it is used as decorative stone, in landscaping, lapidary arts, and stone tumbling.

Geological facts

Chert and jasper are varieties of microcrystalline quartz. Jasper specifically refers to the opaque, iron-rich, colorful varieties, while chert often refers to duller or grey/brown varieties.

Field identification & locations

Identified in the field by its high hardness (cannot be scratched by steel), sharp edges when broken, waxy luster, and smooth conchoidal fracture surfaces. Commonly found along riverbeds, gravel bars, and sedimentary rock formations.