metamorphic
Tiger's Eye
Pseudomorph of quartz after crocidolite (SiO2)
Hardness: 6.5-7 Mohs scale; Color: Golden yellow to deep brown; Luster: Silky; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64-2.71. Known for its strong chatoyancy (cat's-eye effect).
- Hardness
- 6
- Color
- Golden yellow to deep brown
- Luster
- Silky
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Physical properties
Hardness: 6.5-7 Mohs scale; Color: Golden yellow to deep brown; Luster: Silky; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64-2.71. Known for its strong chatoyancy (cat's-eye effect).
Formation & geological history
Formed through the pseudomorphism of crocidolite (blue asbestos) by silica (quartz). Over millions of years, the iron in the crocidolite oxidizes to create the golden-brown color while maintaining the original fibrous structure. Most deposits are Proterozoic in age.
Uses & applications
Primarily used in jewelry (cabochons, beads, pendants) and ornamental carvings. It is also used as a gemstone in 'metaphysical' practices and as a decorative stone in high-end surfacing.
Geological facts
Tiger's Eye is a classic example of a pseudomorph, where one mineral replaces another while retaining the original mineral's shape. It was once considered a precious stone and was very expensive until large deposits were found in South Africa in the 19th century.
Field identification & locations
Identify by its 'chatoyancy' which causes a shimmering band of light to move across the surface as the stone is tilted. It is most commonly found in South Africa, Western Australia, India, and Namibia. Collectors look for sharp, distinct bands and a high polish.
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