sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown/tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown/tan
Luster: Waxy to dull

Identified May 27, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown/tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the precipitation of silica from groundwater or the accumulation of silica-rich organic remains (like radiolarians) in deep-sea environments. Often found as nodules in limestone or as distinct bedded layers.

Uses & applications

Historically used for stone tools (flintknapping); currently used in jewelry (as jasper), landscaping, and as an abrasive in industrial applications.

Geological facts

Chert was one of the first materials used by early humans to create sharp tools and fire-starting kits because of its predictable conchoidal fracturing and hardness.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel nail), smooth waxy texture, and shell-like (conchoidal) fracture patterns. Frequently found in riverbeds or within limestone outcrops.