metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown with silky chatoyancy; Luster: Silky; Crystal structure: Trigonal/Fibrous; Cleavage: None; Specific Gravity: 2.64–2.71
- Hardness
- 6
- Color
- Golden yellow to deep brown with silky chatoyancy
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown with silky chatoyancy; Luster: Silky; Crystal structure: Trigonal/Fibrous; Cleavage: None; Specific Gravity: 2.64–2.71
Formation & geological history
Formed through the pseudomorphism of blue asbestos (crocidolite) fibers. Over millions of years, quartz replaces the crocidolite while retaining the fibrous structure. Primarily found in metamorphosed iron formations dating back to the Proterozoic eon.
Uses & applications
Predominantly used as a gemstone for jewelry (cabochons, beads), decorative carvings, high-end tiling/inlays, and widely collected by mineral enthusiasts for its optical properties.
Geological facts
The distinct 'shimmer' is known as chatoyancy, or the 'cat-eye effect.' While long believed to be a simple replacement process, recent research suggests it may also form through a 'crack-seal' vein mechanism involving simultaneous mineral growth.
Field identification & locations
Identified in the field by its distinct golden-brown bands and the way light reflects off its fibrous interior when rotated. Major deposits are located in South Africa (Griztown), Western Australia, India, and Namibia.
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