sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Tan, brown, ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Tan, brown, ochre
Luster: Waxy to dull

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Tan, brown, ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or groundwater environments; often associated with limestone or replacement in sedimentary beds.

Uses & applications

Historically used for stone tools/arrowheads; currently used in landscaping, as a gemstone when colorful (Jasper), and as a structural aggregate in construction.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces razor-sharp edges. It is chemically identical to quartz but has a different micro-structure.

Field identification & locations

Identify by its hardness (scratches glass), waxy luster, and shell-like (conchoidal) fracture pattern. Found globally in riverbeds, glacial tills, and sedimentary outcrops.