metamorphic
Polished tiger iron
Tiger iron; quartz (SiO₂) with hematite/magnetite and crocidolite-derived riebeckite/goethite
AI-generated identification · may be incorrectHardness about 6.5–7; opaque reddish-brown, gray-black, and golden-brown banding with a vitreous to silky polish. Composed of interlayered quartz, iron oxides, and fibrous amphibole; no obvious cleavage in the finished cabochon.
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Physical properties
Hardness about 6.5–7; opaque reddish-brown, gray-black, and golden-brown banding with a vitreous to silky polish. Composed of interlayered quartz, iron oxides, and fibrous amphibole; no obvious cleavage in the finished cabochon.
Formation & geological history
A banded iron-rich metamorphic rock formed from ancient chemical sediments and altered siliceous iron formations, commonly around 2.5–1.8 billion years old. The golden bands reflect oxidized iron-rich material and altered crocidolite.
Uses & applications
Cut and polished for cabochons, beads, carvings, and ornamental objects; occasionally used as a lapidary stone rather than in construction.
Geological facts
Its distinctive “tiger” pattern combines chatoyant-looking golden bands with red jasper-like and black hematite-rich layers. It is closely related to banded iron formation and is especially associated with Australian material.
Field identification & locations
Identify it by strong red-gold-black parallel bands, opaque stone, and hardness sufficient to scratch ordinary glass; distinguish it from tiger’s-eye, which is usually mostly golden-brown and visibly chatoyant. Major sources include Western Australia, especially the Pilbara region.
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