sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Opaque brown, yellow, and tan with waxy to dull luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 6
Color: Opaque brown, yellow, and tan with waxy to dull luster

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Opaque brown, yellow, and tan with waxy to dull luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation from silica-rich fluids within sedimentary rock layers. Often found in nodules or bedded deposits.

Uses & applications

Historically used for stone tools and weapons due to sharp edges when fractured. Modern uses include jewelry lapidary, landscaping, and it is a common collector specimen.

Geological facts

Chert is so durable that it can survive long periods of weathering and transport in rivers. Jasper is the name specifically given to opaque, iron-stained varieties of chert.

Field identification & locations

Identify by its 'flint-like' behavior: look for smooth, curved (conchoidal) breaks that resemble glass and a waxy surface texture. Very common in gravel pits and riverbeds globally.