sedimentary

Polished banded chert or jasper

Microcrystalline quartz (SiO₂), commonly chalcedony with iron-oxide impurities

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, opaque to slightly translucent, with brown, black, cream, and reddish bands; vitreous to waxy luster and no visible cleavage. The rounded, polished surface obscures its original texture, but the banding suggests layered silica-rich material.

Identified August 17, 2026More sedimentary →

Explore Polished banded chert or jasper in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Forms when silica-rich groundwater or marine fluids replace and cement fine sediments, often in layers; iron and manganese create the dark and brown colors. Exact age cannot be determined from the photograph; chert and jasper range from Precambrian to recent deposits.

Uses & applications

Used for ornamental stone, cabochons, beads, carvings, polished display pieces, and historically as a tool-making material. It has little architectural use compared with ordinary chert.

Geological facts

The specimen may be called “picture jasper” if its bands form scenic patterns, though true jasper and chert can be difficult to distinguish visually. A fresh edge should fracture conchoidally and may reveal a fine, glassy texture.

Field identification & locations

Common in sedimentary formations, volcanic cavities, and replacement deposits worldwide, especially in the western United States, Brazil, Madagascar, and Australia. Test carefully with a steel file: genuine quartz-rich material resists scratching; a vinegar test is irrelevant.