metamorphic
Polished tiger’s-eye
Quartz variety: fibrous golden-brown chalcedonic quartz, SiO₂
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; golden-brown to dark-brown silky bands, vitreous-to-waxy luster, and chatoyancy (cat’s-eye sheen) from aligned fibers. Massive, microcrystalline structure with no visible cleavage; specific gravity about 2.6–2.7.
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Physical properties
Hardness about 6.5–7 Mohs; golden-brown to dark-brown silky bands, vitreous-to-waxy luster, and chatoyancy (cat’s-eye sheen) from aligned fibers. Massive, microcrystalline structure with no visible cleavage; specific gravity about 2.6–2.7.
Formation & geological history
Forms when crocidolite asbestos fibers are replaced by quartz during low-grade metamorphism, commonly in altered iron-rich rocks. Much material formed in the Precambrian, especially in southern Africa.
Uses & applications
Used for cabochons, carvings, beads, ornamental stones, and polished display pieces; rarely used architecturally. Common specimens typically have modest collector value.
Geological facts
The optical “flash” shifts as the stone is rotated, caused by reflection from parallel fibers. Blue-gray hawk’s-eye may represent an incompletely altered stage, while red material is often heat-treated.
Field identification & locations
Identify it by its parallel chatoyant bands, hardness, and resistance to scratching by steel; glassy look-alikes lack the characteristic silky banding. Major sources include South Africa, Western Australia, India, and Brazil.
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