sedimentary

Concretion or weathered iron-rich nodule

Likely an ironstone/siderite–goethite concretion; exact identification requires testing

AI-generated identification · may be incorrect

Rounded, dense, brown-gray, dull to earthy luster with a prominent fracture or seam and rough weathered surface. Likely Mohs hardness ~4–6; composition and specific gravity are uncertain from the image, but iron-rich concretions are typically heavy and non-cleavable.

Identified August 24, 2026More sedimentary →

Explore Concretion or weathered iron-rich nodule 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

Probably formed when iron-bearing minerals cemented sediment around a nucleus, later exposed and weathered; commonly Cenozoic or Mesozoic, though age depends on its host formation. It could also be a naturally rounded ironstone cobble or an unusual meteorite, but appearance alone cannot confirm either.

Uses & applications

Usually collected as a geological curiosity or used educationally; it has little industrial or jewelry value unless unusually patterned or proven meteoritic.

Geological facts

Iron-rich surfaces may develop red-brown goethite or hematite staining. A strong magnet, unusually high density, and a fresh interior can help distinguish ironstone from ordinary sedimentary concretions.

Field identification & locations

Look for similar rounded nodules in clay, shale, river gravels, and ironstone beds. Test magnetism, streak on unglazed porcelain, density, and a freshly broken surface; avoid cutting until provenance is known.