sedimentary

Jasper

Silicon dioxide (SiO2) with iron oxide impurities

Hardness: 6.5–7 on Mohs scale; Color: Dark brown/ochre with mottled pattern; Luster: Dull to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.91

Hardness: 6
Color: Dark brown/ochre with mottled pattern
Luster: Dull to waxy

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the deposition of silica from water-rich environments or volcanic ash. The brown color indicates a high concentration of iron oxides (goethite or limonite). These specimens can range from the Cretaceous to much older Paleozoic eras.

Uses & applications

Commonly used in lapidary work for cabochons, beads, and ornamental carvings. Historically used for making tools due to its sharp conchoidal fracture.

Geological facts

Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone'. It is known for its incredible variety of patterns and colors caused by mineral inclusions.

Field identification & locations

Identify in the field by its hardness (will scratch glass), opaque nature (unlike translucent agate), and smooth, curved fracture surfaces. Often found as river-worn pebbles in regions with volcanic or sedimentary history.

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