sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Brown/Ochre, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.8

Hardness: 6

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Brown/Ochre, Luster: Waxy to dull, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.8

Formation & geological history

Formed via the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine or lacustrine settings where silica replaces limestone or chalk.

Uses & applications

Historically used for stone tools (knapping) due to its sharp fracture edges. Today used in jewelry, lapidary arts as jasper, and as an industrial abrasive.

Geological facts

Chert has been used by humans for millions of years to create arrowheads and scrapers. The brown/red varieties are specifically known as jasper when they contain iron oxide impurities.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Found globally in nodules within limestone or as bedded deposits.