sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Reddish-brown, gray, tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Reddish-brown, gray, tan
Luster: Dull to waxy

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Reddish-brown, gray, tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments, often deep sea or limestone replacement. Found across all geological ages.

Uses & applications

Historically used for stone tools (arrowheads). Currently used for lapidary work, jewelry, landscaping, and construction aggregate.

Geological facts

Red specimens are often referred to as Jasper. Because of its conchoidal fracture, it was one of the most important materials for early humans to create sharp-edged tools.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and smooth, curved (conchoidal) breaks. Commonly found in riverbeds or as nodules in limestone.