sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Dark brown, tan, and yellowish patches; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 6
Color: Dark brown, tan, and yellowish patches
Luster: Waxy to vitreous

Identified May 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine environments. This specimen appears to be water-worn jasper, commonly found in river beds or glacial till.

Uses & applications

Used for decorative stones, lapidary work (polishing and jewelry), and historically for tool making (arrowheads/scrapers) due to its sharp edges when broken.

Geological facts

Jasper is an opaque variety of chert. The distinct patterns and colors are caused by iron oxides and other mineral impurities trapped during the formation process.

Field identification & locations

Identify in the field by its smooth, waxy texture, conchoidal (shell-like) fracture patterns, and extreme hardness (it will scratch glass). Often found as rounded pebbles in gravel deposits.