mineral
Polished ironstone or hematite-rich river pebble
Ironstone, likely hematite/goethite-bearing quartz or chert (Fe₂O₃/FeO(OH) with silica)
AI-generated identification · may be incorrectHardness commonly 5–6.5 Mohs; brown, reddish-brown, gray, and metallic patches with a smooth polished luster. Dense, fine-grained, and non-cleavable; exact composition requires streak, magnetism, and specific-gravity tests.
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Physical properties
Hardness commonly 5–6.5 Mohs; brown, reddish-brown, gray, and metallic patches with a smooth polished luster. Dense, fine-grained, and non-cleavable; exact composition requires streak, magnetism, and specific-gravity tests.
Formation & geological history
Formed by iron-oxide cementation or weathering of iron-rich sediments, then naturally water-rounded and possibly hand-polished; age is indeterminate and depends on its source formation.
Uses & applications
Used as ornamental stone, lapidary material, pigment source, and occasionally as iron ore; generally not a gemstone unless strongly patterned or unusually lustrous.
Geological facts
A reddish-brown streak on unglazed porcelain supports hematite, while yellow-brown coatings suggest goethite/limonite. Strong magnetism would indicate magnetite or maghemite instead.
Field identification & locations
Common in river gravels and iron-rich terrains worldwide, including Australia, Brazil, India, and the Lake Superior region. Field identification relies on high density, earthy red-brown streak, and absence of visible crystals.
