sedimentary

Rounded iron-rich concretion or weathered lateritic pebble

Goethite/hematite-bearing ferruginous concretion; exact mineralogy requires testing

AI-generated identification · may be incorrect

Smooth, brown-orange, dull to weakly earthy luster, apparently massive and fine-grained with no visible crystals or cleavage. Likely hardness about 4–6 Mohs; streak may be yellow-brown to reddish-brown, and specific gravity commonly about 3–4 if strongly iron-rich.

Identified September 2, 2026More sedimentary →

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At a glance

Common name: Rounded iron-rich concretion or weathered lateritic pebble
Scientific name: Goethite/hematite-bearing ferruginous concretion; exact mineralogy requires testing
Category: sedimentary
Identified: September 2, 2026
Method: Standard

AI Estimated Value

Typically $1–$10 as a common unverified pebble; up to about $20 if unusually dense, attractive, or locality-documented.

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

Formed by weathering and concentration of iron oxides/hydroxides in tropical soils or sediment, followed by rounding by transport. Such material is common in lateritic terrains around southeastern Brazil, including the São Paulo coastal region; age is usually relatively young and not determinable from appearance.

Uses & applications

Primarily a natural curiosity or teaching/collection specimen; iron-rich material can contribute to iron ore, pigments, and aggregate, but this individual pebble has little industrial value.

Geological facts

The glossy appearance is likely natural smoothing rather than crystal luster. A streak test and magnet test can distinguish iron-rich concretion from ordinary brown chert or quartzite.

Field identification & locations

Field identification: unusually dense, opaque, rusty-brown pebble with earthy red-brown streak and possible weak magnetism. If it scratches glass, chert is more likely; if it leaves a strong ochre streak, goethite/hematite-rich material is favored.