mineral

Tumbled jasper or iron-rich chert

Microcrystalline quartz (SiO₂) with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; mustard yellow, brown, gray, and reddish coloration with an opaque, waxy-to-subvitreous luster. It has cryptocrystalline quartz structure, no visible cleavage, and conchoidal fracture; the smooth surface indicates tumbling or natural abrasion.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids replaced or cemented sediment, with iron oxides producing the yellow-brown colors. Such material commonly formed in Paleozoic–Mesozoic volcanic or sedimentary environments, though the specimen’s exact age cannot be determined visually.

Uses & applications

Used as a low-cost ornamental stone for cabochons, beads, carvings, and tumbled specimens; occasionally used in decorative stonework.

Geological facts

The specimen may be jasper, chert, or a closely related iron-rich quartz variety; these names often overlap commercially. Strong red streaks usually indicate hematite, while yellow-brown tones commonly reflect limonite/goethite.

Field identification & locations

Commonly found in sedimentary and volcanic terrains worldwide, especially regions of the western United States, Australia, Brazil, and India. A glass-scratch test and absence of fizz in dilute acid support quartz-rich material, but testing may damage it.