sedimentary

Jasper (Chert)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, yellow, and black; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91

Hardness: 6
Color: Variegated brown, yellow, and black
Luster: Dull to waxy

Identified July 17, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, yellow, and black; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91

Formation & geological history

Formed from the chemical precipitation of silica-rich fluids in volcanic or sedimentary environments. The specific coloration is caused by iron oxides (limonite/hematite) and other mineral impurities during formation.

Uses & applications

Used primarily as a decorative stone, in lapidary arts for cabochons and beads, and as a collector's specimen.

Geological facts

Jasper is an opaque variety of chalcedony. It has been used by ancient civilizations for making tools and seals because it is hard and breaks with sharp edges.

Field identification & locations

Identify by its opacity, extreme hardness (it will scratch glass), and smooth water-worn texture when found in riverbeds. Common in glacial till and river deposits worldwide.