mineral

Tumbled jasper or iron-rich chert

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; reddish-brown to gray, opaque, with a waxy-to-dull luster and conchoidal fracture. The rounded, polished surface suggests a tumbled or naturally water-worn specimen; crystal grains are microscopic.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or fill cavities in volcanic or sedimentary rocks, with iron oxides producing the red-brown color. Formation ages vary widely, commonly from Paleozoic to Cenozoic deposits.

Uses & applications

Used for cabochons, carvings, beads, lapidary work, and decorative specimens; ordinary pieces generally have modest commercial value.

Geological facts

Jasper is a variety of opaque chalcedony, while chert is the broader fine-grained silica category; visual separation is often difficult without locality information or testing.

Field identification & locations

Common in volcanic terrains, sedimentary beds, and gravel deposits worldwide, especially the western United States, Brazil, Madagascar, and Australia. A steel file should not easily scratch it, and it will not show visible cleavage.