sedimentary

Chert (specifically brown Chert or Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Dark brown to reddish-brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (has conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 Mohs scale
Color: Dark brown to reddish-brown
Luster: Waxy to dull

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Dark brown to reddish-brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (has conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or through the chemical precipitation of silica in sedimentary environments. Common in marine limestone formations.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges when fractured. Currently used in lapidary work, jewelry (especially when colorful like Jasper), and as architectural aggregate.

Geological facts

Chert is one of the most durable sedimentary rocks. It was historically valuable for striking fire against steel, similar to flint. It is also a very common rock found in riverbeds and glacial deposits.

Field identification & locations

Identified in the field by its conchoidal (shell-like) fracture, waxy luster, and its ability to scratch glass. Found globally in creek beds, beaches, and sedimentary outcrops.