sedimentary

Chert (Jasper and Chalcedony)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, white, and reddish-brown, Luster: waxy to dull, Crystal structure: microcrystalline/cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.58–2.91

Hardness: 6

Identified May 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary rock layers, often found in limestone or volcanic ash deposits.

Uses & applications

Historically used for stone tools and arrowheads; currently used for lapidary work, jewelry (cabs), and as decorative landscape stones.

Geological facts

This specimen shows the transition between common chert and red jasper. Jasper gets its red color from iron inclusions. Because of its conchoidal fracture, it was one of the most important materials for early human technology.

Field identification & locations

Identify in the field by its hardness (will scratch steel), waxy luster on fresh surfaces, and scalloped conchoidal fractures. Commonly found in river beds or erosion zones near limestone outcrops.