metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxides)
Hardness: 7 (Mohs); Color: Golden-brown to yellow-gold; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None (fractures); Specific Gravity: 2.64–2.71
- Hardness
- 7 (Mohs)
- Color
- Golden-brown to yellow-gold
- Luster
- Silky
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Physical properties
Hardness: 7 (Mohs); Color: Golden-brown to yellow-gold; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None (fractures); Specific Gravity: 2.64–2.71
Formation & geological history
Formed when quartz replaces the fibrous mineral crocidolite (asbestos) through a process of pseudomorphism, where the original fibrous structure is retained. Found in Precambrian metamorphic rocks, often over 2 billion years old.
Uses & applications
Widely used in jewelry (cabochons, beads), decorative carvings, and as a popular semi-precious stone for collectors due to its unique optical properties.
Geological facts
Exhibits a distinct optical effect known as chatoyancy, where a silky band of light moves across the stone as it is turned. While it begins as hazardous blue asbestos, the quartz replacement makes it safe to handle.
Field identification & locations
Identify in the field by its distinct golden-brown bands and 'cat's-eye' light reflection. Common locations include South Africa (Northern Cape), Western Australia, India, and the USA (California/Arizona).
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