sedimentary

Jasper (River pebble)

Jasper / Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brownish-purple with grey mottling; Luster: Dull to waxy; Crystal Structure: Microcrystalline/cryptocrystalline (hexagonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91

Hardness: 6
Color: Brownish-purple with grey mottling
Luster: Dull to waxy

Identified March 29, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the infiltration of silica-rich fluids into sediment or volcanic ash, which then hardens over millions of years. This specific specimen has been chemically changed and then physically rounded by alluvial (river) water action.

Uses & applications

Common varieties are used for jewelry (cabochons), lapidary art, tumble-polishing, and as decorative gravel in landscaping.

Geological facts

Jasper is an opaque variety of chalcedony. The name 'jasper' comes from the Old French word 'jaspre', meaning 'spotted or speckled stone'. No two pieces are identical because of the unique inclusion of minerals like iron oxides.

Field identification & locations

Identify in the field by its opacity (it does not let light through even at thin edges) and its smooth, water-worn surface when found in riverbeds. Common in rocky riverbanks and coastal areas worldwide.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone (Quartz-rich)

Arenite (SiO2)

sedimentary

Sandstone (with man-made markings)

Arenite (composed primarily of Quartz, SiO2)

sedimentary