mineral
Polished hematite-rich ironstone
Hematite (Fe₂O₃), likely mixed with magnetite and iron-rich jasper
AI-generated identification · may be incorrectHardness about 5–6.5 Mohs; metallic to submetallic luster, black with red-brown earthy patches, massive rather than visibly crystalline, and very high density (about 4.5–5.3). The smooth reflective surface appears naturally weathered or polished.
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Physical properties
Hardness about 5–6.5 Mohs; metallic to submetallic luster, black with red-brown earthy patches, massive rather than visibly crystalline, and very high density (about 4.5–5.3). The smooth reflective surface appears naturally weathered or polished.
Formation & geological history
Formed through oxidation and concentration of iron in ancient sedimentary or hydrothermal deposits; associated jasper may be Precambrian in age. Ironstones commonly develop red hematite zones around darker magnetite-rich material.
Uses & applications
Used chiefly as an iron ore, pigment, lapidary material, and collector specimen; attractive polished pieces are sold as ornamental stones rather than gemstones.
Geological facts
The red streak of hematite is diagnostic, even when the specimen looks black; magnetite-rich portions may attract a strong magnet. It is not possible to confirm exact identity from appearance alone.
Field identification & locations
Common in banded iron formations and weathered iron deposits worldwide, especially Australia, Brazil, India, and North America. Test an inconspicuous area for a red-brown streak and measure magnetism; avoid damaging valuable polish.
