sedimentary

Concretion, likely ironstone or sandstone concretion

Diagenetic mineral concretion, commonly quartz/calcite cement with iron oxides (goethite/hematite)

AI-generated identification · may be incorrect

Brown, roughly spherical, earthy to dull luster, fine-grained and noncrystalline externally; likely Mohs 4–6 depending on cement, with no obvious cleavage. The surface appears weathered and iron-stained, though the image cannot confirm internal composition.

Identified August 24, 2026More sedimentary →

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At a glance

Common name: Concretion, likely ironstone or sandstone concretion
Scientific name: Diagenetic mineral concretion, commonly quartz/calcite cement with iron oxides (goethite/hematite)
Category: sedimentary
Identified: August 24, 2026
Method: Standard

AI Estimated Value

Typically $5–$30 for a common specimen; up to $50–$150 for unusually shaped, large, or well-displayed examples.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Forms when minerals precipitate around a nucleus within sediment during diagenesis, producing a resistant rounded mass; commonly Cenozoic to Mesozoic, but age depends on its host formation. Natural abrasion may further round exposed concretions.

Uses & applications

Usually collected as a geological curiosity or used for educational displays; generally unsuitable for jewelry or construction unless exceptionally large or attractive.

Geological facts

Concretions can resemble meteorites, but terrestrial concretions commonly show earthy texture, porous weathering, and iron-oxide staining rather than a fusion crust or metallic interior.

Field identification & locations

Look for concentric structure or a contrasting cemented interior when broken, and test streak, magnetism, hardness, and density; common in sedimentary outcrops, beaches, deserts, and stream gravels. A definitive identification requires a fresh surface or laboratory testing.