sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, red, and dark grey; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Fractures with conchoidal (shell-like) curves.

Hardness: 6
Color: Brown, red, and dark grey
Luster: Dull to waxy

Identified July 16, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, red, and dark grey; Luster: Dull to waxy; Structure: Microcrystalline/cryptocrystalline; Fractures with conchoidal (shell-like) curves.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows iron staining (red/brown) and high silica content.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges; currently used as decorative stone, in jewelry (when high quality), and as road ballast.

Geological facts

Chert was one of the most important minerals for early humans, used to create arrowheads, scrapers, and fire-starting tools because it sparks when struck against steel.

Field identification & locations

Look for a smooth, waxy texture and sharp, curved edges where broken. It cannot be scratched by a steel pocket knife. Found globally in limestone formations and riverbeds.