sedimentary

Tumbled jasper pebble

Chalcedony-rich microcrystalline quartz (SiO₂), commonly called brown or brecciated jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, reddish-brown, tan, and cream coloration with earthy to dull luster. It has a cryptocrystalline quartz structure, no visible cleavage, and typically conchoidal fracture; the rounded shape indicates natural water wear or tumbling.

Identified September 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Jasper forms when silica-rich fluids replace or cement volcanic ash, sediment, or fragmented rock, often with iron oxides producing red-brown colors. Formation ages vary widely, from Precambrian to younger volcanic and sedimentary settings.

Uses & applications

Used for cabochons, beads, carvings, decorative objects, and lapidary specimens; historically used for tools and ornamental stone. It has little construction value compared with common aggregate.

Geological facts

Iron-oxide staining creates the warm red and brown patterns. The specimen’s smooth, waterworn appearance and opaque fine-grained texture distinguish it from transparent agate or crystalline quartz.

Field identification & locations

Identify by its opaque body, waxy-to-earthy surface, hardness, lack of cleavage, and inability to scratch with a steel knife easily; common sources include India, Madagascar, Brazil, Mexico, and the western United States.