sedimentary

Jasper

Silicon dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91

Hardness: 6
Color: Brown, tan, reddish-brown
Luster: Dull to waxy

Identified March 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the infiltration of silica-rich fluids into volcanic ash or fine-grained sediments. Over time, these fluids solidify into a dense, opaque variety of chalcedony. The brown colors are typically due to iron oxides (like goethite or limonite).

Uses & applications

Used primarily as a gemstone for jewelry (cabochons), lapidary art, ornaments, and historical tools like scrapers and arrowheads due to its hardness.

Geological facts

Jasper is an opaque variety of chalcedony. The name 'jasper' comes from the Greek word 'iaspis', meaning 'spotted stone.' Some varieties are so distinct they are named after their location, like Owyhee Jasper or Mookaite.

Field identification & locations

Identify in the field by its opaque nature (unlike translucent agate), conchoidal fracture (curved breaks), and the fact that it cannot be scratched by a steel knife. Frequently found in riverbeds, deserts, and volcanic regions.