mineral

Iron-rich concretion or slag-like mineral fragment

Likely limonite/goethite (FeO(OH)·nH₂O), possibly magnetite-bearing material

AI-generated identification · may be incorrect

Dark brown-black, dull to submetallic luster, irregular botryoidal surface with rusty tan weathering; hardness about 4–6 Mohs, no obvious cleavage, and relatively high specific gravity. The image is insufficient to confirm crystal structure or metallic iron.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed by oxidation and precipitation of iron-bearing minerals in soil, fractures, or sediment; it may also be anthropogenic iron slag. Age and geological setting cannot be determined from the photograph.

Uses & applications

Common iron oxides are ores and pigments, but this small specimen has mainly educational or collector interest rather than commercial value.

Geological facts

Goethite and limonite commonly produce yellow-brown to black earthy coatings and nodules; magnetite-bearing pieces may attract a magnet.

Field identification & locations

Look for a rusty streak on unglazed porcelain, strong heft, and possible magnetism; a metallic streak or vesicular texture would suggest slag. Common in weathered iron-rich rocks worldwide.