sedimentary

Chert (and Jasper) Nodules in Limestone

Silicon Dioxide (SiO2) microcrystalline quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Brownish-red (Jasper) with greyish-blue (Chert) interior, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Brownish-red (Jasper) with greyish-blue (Chert) interior, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)

Formation & geological history

Formed through the accumulation of silica-rich fluids within sedimentary rock layers, often replacing carbonate material or filling voids in limestone. This process typically occurs in marine environments over millions of years.

Uses & applications

Historically used for making stone tools (flint knapping) due to its sharp edges; used today as a decorative stone, in lapidary work, and sometimes as an abrasive.

Geological facts

Chert and its red variety, Jasper, have been used by humans for hundreds of thousands of years to create arrowheads and scrapers because they break with predictable, razor-sharp conchoidal fractures.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, shell-like fracture pattern. Often found as nodules or layers within limestone or chalk beds.