sedimentary

Tumbled brown stone, likely chert or jasper

Microcrystalline quartz (SiO₂), likely ferruginous chert/jasper

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, opaque brown to reddish-brown, with dull to waxy luster and no visible cleavage; compact microcrystalline quartz structure. The smoothly rounded surface indicates natural water wear or tumbling.

Identified September 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediment, with iron oxides producing the brown-red color; exact age and locality cannot be determined from the image. Common in gravel deposits and weathered sedimentary terrains.

Uses & applications

Used as a durable lapidary material for cabochons, carvings, beads, and decorative stones; less commonly used as aggregate. Its value is mainly ornamental.

Geological facts

Chert and jasper are varieties of microcrystalline quartz; jasper is generally opaque and impurity-rich, while chert may be gray, brown, or multicolored. The specimen could also be another iron-stained quartz-rich pebble.

Field identification & locations

Identify by its glassy-to-waxy appearance, exceptional resistance to scratching, and inability to scratch with a steel nail easily; a streak, hardness, and specific-gravity test would help distinguish it from ordinary sandstone or slag. Found worldwide, especially in river gravels.