mineral
Likely tumbled hematite-rich ironstone
Hematite, Fe₂O₃, possibly mixed with goethite or magnetite
AI-generated identification · may be incorrectSmall rounded, polished dark gray-brown specimen with metallic to submetallic luster and reddish-brown streak potential; hematite hardness is 5–6.5 Mohs, with no prominent cleavage and a trigonal crystal structure.
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Physical properties
Small rounded, polished dark gray-brown specimen with metallic to submetallic luster and reddish-brown streak potential; hematite hardness is 5–6.5 Mohs, with no prominent cleavage and a trigonal crystal structure.
Formation & geological history
Iron oxides form through oxidation, weathering, hydrothermal activity, or sedimentary concentration of iron; the specimen was likely naturally rounded and subsequently tumbled or polished. Exact geological age cannot be determined from the image.
Uses & applications
Used as an iron ore, pigment, polishing compound, and ornamental stone; common tumbled pieces have modest collector value.
Geological facts
A diagnostic hematite streak is red to reddish-brown, even when the surface appears metallic black. Strong magnetism would suggest magnetite or a mixture rather than pure hematite.
Field identification & locations
Common worldwide, especially in banded iron formations and weathered iron-rich deposits; major sources include Brazil, Australia, South Africa, and the Lake Superior region. Test streak on unglazed ceramic and magnetism, but avoid scratching valuable surfaces.
