sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, earthy tones; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65

Hardness: 6
Color: Reddish-brown, earthy tones
Luster: Waxy to dull

Identified July 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary basins. Red hues often indicate iron oxide inclusions (hematite). Many specimens are hundreds of millions of years old.

Uses & applications

Historically used for stone tools (flintknapping) due to sharp fracture edges. Modern use in lapidary work, jewelry, and as landscaping stones.

Geological facts

Usually referred to as 'Jasper' when opaque and red/brown. It is one of the most common materials used by early humans for arrowheads and scrapers because of its predictable breaking patterns.

Field identification & locations

Look for a smooth, waxy surface and conchoidal (shell-like) fractures. It will scratch glass but cannot be scratched by a steel knife. Common in gravel beds and desert environments worldwide.