metamorphic
Polished tiger iron cabochon
Banded iron formation (BIF), chiefly hematite/magnetite, jasper, and tiger’s-eye quartz
AI-generated identification · may be incorrectHardness is approximately 6.5–7 overall; metallic to silky and earthy luster with reddish-brown, golden, gray, and black bands. The bands reflect quartz-rich jasper alternating with iron oxides and may show chatoyancy from fibrous quartz; cleavage is absent and specific gravity is commonly about 2.8–3.3.
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Physical properties
Hardness is approximately 6.5–7 overall; metallic to silky and earthy luster with reddish-brown, golden, gray, and black bands. The bands reflect quartz-rich jasper alternating with iron oxides and may show chatoyancy from fibrous quartz; cleavage is absent and specific gravity is commonly about 2.8–3.3.
Formation & geological history
Formed from ancient chemical sediments and later metamorphosed, commonly during the Precambrian (roughly 2.5–1.8 billion years ago). Tiger’s-eye layers formed when crocidolite fibers were replaced by quartz and iron oxides during alteration.
Uses & applications
Used for cabochons, beads, carvings, display pieces, and ornamental objects; it is generally unsuitable for structural construction because it is sold as a decorative stone.
Geological facts
Its striking stripes combine the jasper and iron-oxide components of tiger iron with chatoyant tiger’s-eye layers. The visible pattern is natural banding, enhanced by cutting and polishing.
Field identification & locations
Identify it by dense parallel bands, strong polish, earthy iron colors, and occasional silky golden chatoyancy; it is commonly associated with deposits in Western Australia and South Africa. A polished rectangular cabochon typically sells for about $10–$50, with exceptional pieces reaching $75–$150.
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