mineral
Ironstone / limonitic iron ore
Goethite–hematite–limonite aggregate, chiefly FeO(OH) and Fe₂O₃·nH₂O
AI-generated identification · may be incorrectHardness about 5–6.5 Mohs; rusty orange-brown, earthy to dull submetallic luster, massive and fine-grained, with no visible cleavage. The dark gray patches may be hematite or magnetite; it may leave a yellow-brown to red streak and commonly feels dense.
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Physical properties
Hardness about 5–6.5 Mohs; rusty orange-brown, earthy to dull submetallic luster, massive and fine-grained, with no visible cleavage. The dark gray patches may be hematite or magnetite; it may leave a yellow-brown to red streak and commonly feels dense.
Formation & geological history
Forms through oxidation and weathering of iron-bearing rocks or sulfide deposits, often as lateritic ironstone or a gossan. Such material can form at any age near Earth’s surface; the specimen’s age cannot be determined from the image.
Uses & applications
Used as iron ore when sufficiently rich, and as a pigment or lapidary/collector material. It is generally more valued for attractive texture than for jewelry.
Geological facts
The orange color reflects hydrated iron oxides, while darker areas commonly indicate hematite or magnetite. A strong magnet response would suggest magnetite-rich material, but weak or absent magnetism is typical of limonite/goethite.
Field identification & locations
Identify by its rusty color, high density, earthy texture, and red-yellow streak; a streak test and magnet test are useful. Common in weathered iron deposits, laterites, and mine gossans worldwide.
