metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxide inclusions)
Hardness: 6.5-7.0 (Mohs scale); Color: Golden yellow to brown/black bands; Luster: Silky; Crystal structure: Trigonal (fibrous texture); Cleavage: None; Specific gravity: 2.64-2.71.
- Hardness
- 6
- Color
- Golden yellow to brown/black bands
- Luster
- Silky
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Golden yellow to brown/black bands; Luster: Silky; Crystal structure: Trigonal (fibrous texture); Cleavage: None; Specific gravity: 2.64-2.71.
Formation & geological history
Formed through the metamorphic process where quartz replaces the fibrous mineral crocidolite (blue asbestos) while retaining the original fibrous structure. Most deposits are Proterozoic in age (approx. 2 billion years old).
Uses & applications
Extensively used in jewelry (cabochons, beads), decorative carvings, and as a popular semi-precious gemstone for collectors.
Geological facts
Exhibits chatoyancy (the 'cat's eye' effect) due to the parallel orientation of internal fibers. Historically, it was worn by Roman soldiers in battle for protection and courage.
Field identification & locations
Identify by its alternating bands of gold and dark brown and its distinct silky shimmering effect when tilted under light. Commonly found in South Africa (Griquatown) and Western Australia.
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