metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Golden-brown to yellow with dark stripes; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None (conchoidal fracture); Specific gravity: 2.64–2.71
- Hardness
- 6
- Color
- Golden-brown to yellow with dark stripes
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Golden-brown to yellow with dark stripes; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None (conchoidal fracture); Specific gravity: 2.64–2.71
Formation & geological history
Formed as a pseudomorph through the replacement of fibrous crocidolite (blue asbestos) with silica/quartz. The original fibrous structure is retained through the replacement process, leading to the chatoyant effect. Major deposits are found in Precambrian banded iron formations.
Uses & applications
Primarily used in jewelry (cabochons, beads, and pendants), decorative ornaments, carvings, and as a popular specimen for crystal collectors.
Geological facts
Tiger's Eye is famous for its 'chatoyancy' or cat's-eye effect. It was originally believed that the blue crocidolite fibers were completely replaced by quartz, but modern research suggests a 'crack-seal' mechanism where quartz grows between crocidolite fibers.
Field identification & locations
Identify in the field by its distinct bands of golden-yellow light that seem to move as the stone is tilted (chatoyancy). It is commonly found in South Africa (Northern Cape), Western Australia, India, and Namibia.
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