sedimentary

Jasper

Silicon dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown due to iron inclusions; Luster: Dull to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.91.

Hardness: 6
Color: Reddish-brown due to iron inclusions
Luster: Dull to vitreous

Identified April 11, 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, the silica crystallizes and incorporates mineral impurities that provide the characteristic color. Most specimens range from millions to hundreds of millions of years old.

Uses & applications

Commonly used for lapidary work, cabochons, beads for jewelry, and ornamental stones. Historically used for making tools like scrapers and arrowheads due to its hardness and sharp fracture edges.

Geological facts

Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone'. It was one of the stones in the breastplate of the Jewish high priest in the Old Testament.

Field identification & locations

Identify in the field by its opaque nature (unlike agate, light will not pass through it even on thin edges) and its smooth, waxy surface when water-worn. Common in riverbeds and coastal regions where volcanic or sedimentary layers have eroded.