sedimentary

Chert / River Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, cream, and olive green with swirling patterns; Luster: Waxy to vitreous; Structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, tan, cream, and olive green with swirling patterns
Luster: Waxy to vitreous

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary layers. This specific water-worn specimen likely originated from Mesozoic or Paleozoic riverbed deposits.

Uses & applications

Used for lapidary work, jewelry making (cabochons), and as landscaping stone. Historically used for making stone tools due to its sharp edges when fractured.

Geological facts

Chert was one of the most important minerals for early humans, used to create arrowheads and scrapers. Its tight crystalline structure makes it incredibly durable against water erosion.

Field identification & locations

Identify by its waxy texture and inability to be scratched by a steel knife. Commonly found in riverbeds, creek bottoms, and glacial till. Look for the smooth, rounded 'river-worn' exterior.