sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Yellow-brown/ochre; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Yellow-brown/ochre
Luster: Dull to waxy

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Yellow-brown/ochre; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich fluids in sedimentary environments or the replacement of limestone. Can range from ancient Precambrian to more recent deposits.

Uses & applications

Used historically for stone tools due to sharp fracture edges. Today used for lapidary work, decorative landscaping, and as a semi-precious gemstone in jewelry.

Geological facts

This specimen shows the typical 'desert varnish' or iron-oxide staining common in cryptocrystalline quartzes. Chert was one of the most important minerals for early humans to create arrowheads and scrapers.

Field identification & locations

Identify in the field by its hardness (will scratch glass), smooth waxy feel when wet, and its characteristic curved (conchoidal) breaks. Often found in riverbeds or as nodules within limestone.