metamorphic
Tiger iron
Banded iron formation (BIF), chiefly hematite/magnetite, jasper, and crocidolite or riebeckite quartz
AI-generated identification · may be incorrectHardness about 6–7 Mohs; distinctive gold-brown, red, gray, and black wavy bands; vitreous to silky luster, dense fine-grained texture, and no obvious cleavage. The dark bands may be weakly magnetic if magnetite-rich.
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Physical properties
Hardness about 6–7 Mohs; distinctive gold-brown, red, gray, and black wavy bands; vitreous to silky luster, dense fine-grained texture, and no obvious cleavage. The dark bands may be weakly magnetic if magnetite-rich.
Formation & geological history
A metamorphosed banded iron formation composed of alternating iron oxides and silica-rich layers, later folded and recrystallized; most commercial material comes from Precambrian deposits roughly 2.5–1.8 billion years old in Western Australia.
Uses & applications
Primarily a lapidary and ornamental stone used for polished slabs, cabochons, spheres, carvings, and jewelry; rarely used as iron ore because attractive specimens are selected for display.
Geological facts
Its tiger-stripe appearance results from strongly contrasting iron-rich and jasper/quartz bands. Crocidolite-bearing varieties can produce chatoyant, golden fibers, although cutting should avoid generating hazardous fibrous dust.
Field identification & locations
Identify it by the parallel-to-wavy metallic black, ochre, and reddish bands, very high density, and possible magnetism; a polished surface reveals the pattern most clearly. Major sources include Western Australia, especially the Pilbara region.
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