metamorphic
Polished tiger iron
Tiger iron: banded quartz–crocidolite/jasper–hematite rock
AI-generated identification · may be incorrectTypically Mohs 6.5–7; brown, gold, cream, and black planar or wavy bands, with vitreous to silky luster. Composed mainly of quartz, iron oxides (hematite/goethite), and altered fibrous amphibole; no consistent cleavage as a whole rock.
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Physical properties
Typically Mohs 6.5–7; brown, gold, cream, and black planar or wavy bands, with vitreous to silky luster. Composed mainly of quartz, iron oxides (hematite/goethite), and altered fibrous amphibole; no consistent cleavage as a whole rock.
Formation & geological history
A Precambrian banded iron formation altered and silicified during metamorphism, commonly dated around 2.2–2.0 billion years old. Polishing reveals its contrasting iron-rich and silica-rich layers.
Uses & applications
Used for cabochons, carvings, beads, ornaments, and lapidary slabs; valued primarily as a decorative stone rather than an industrial material.
Geological facts
The golden chatoyant appearance resembles tiger’s-eye, but tiger iron is a layered rock rather than a single quartz variety. Red-brown bands commonly derive from hematite or jasper.
Field identification & locations
Identify it by straight-to-wavy parallel bands of metallic black, ochre/gold, red-brown, and cream, plus a hard polish; it should scratch glass. Major sources include Western Australia, especially the Pilbara region.
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