sedimentary

Chert (specifically Jasper/Brown Chert)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Brown, earthy ochre, or tan; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Brown, earthy ochre, or tan
Luster: Dull to waxy

Identified March 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, earthy ochre, or tan; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in sedimentary environments. Common in Paleozoic to Cenozoic rock layers.

Uses & applications

Historically used for stone tools/arrowheads due to its sharp edges; modernly used in jewelry (cabochons), landscaping, and as an abrasive in industrial applications.

Geological facts

Chert is so durable that it often survives as stream gravel long after the surrounding rock has eroded. High-quality brown jasper is often referred to as 'Egyptian Marble' or 'Mookite' depending on the specific region and patterns.

Field identification & locations

Identify by its 'flint-like' smooth, curved (conchoidal) breaks and its ability to scratch glass. Commonly found in riverbeds, glacial till, and embedded within limestone or dolomite formations.