sedimentary

Chert (Jasper variation)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, earthy
Luster: Waxy to dull

Identified July 12, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earthy; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone beds and as nodules.

Uses & applications

Historically used for stone tools and arrowheads due to its sharp edges; currently used for lapidary work, jewelry, and as landscaping stone.

Geological facts

Chert is so durable that it often survives as pebbles in stream beds long after the surrounding rock has weathered away. It is chemically identical to quartz but contains impurities that give it color.

Field identification & locations

Identify in the field by its waxy luster, extreme hardness (can scratch glass), and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in gravel pits and desert washes.