metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron inclusions)
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow, brown, and brownish-black stripes; Luster: Silky; Crystal structure: Trigonal (fibrous texture); Cleavage: None; Specific gravity: 2.64–2.71
- Hardness
- 6
- Color
- Golden yellow, brown, and brownish-black stripes
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow, brown, and brownish-black stripes; Luster: Silky; Crystal structure: Trigonal (fibrous texture); Cleavage: None; Specific gravity: 2.64–2.71
Formation & geological history
Formed through the pseudomorphism of blue crocidolite (asbestos) fibers by silica (quartz). While the fibers are replaced by quartz, the silk-like structure is preserved. It is typically found in Precambrian rocks approximately 2 billion years old.
Uses & applications
Primarily used as a semi-precious gemstone in jewelry (cabochons, beads), decorative carvings, and as a popular specimen for mineral collectors due to its unique optical properties.
Geological facts
It exhibits a unique optical phenomenon called chatoyancy (the 'cat's-eye effect'). Historically, it was worn as a protective talisman by Roman soldiers and was considered more valuable than gold in some ancient cultures.
Field identification & locations
Identify in the field by its distinct chatoyancy (shifting bands of light when rotated) and fibrous, banded appearance. It is most famously found in South Africa (Griqualand West) and Western Australia.
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