metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron inclusions)
Hardness: 7 (Mohs scale); Color: Golden yellow to deep brown with silky chatoyant bands; Luster: Silky to vitreous; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64–2.71
- Hardness
- 7 (Mohs scale)
- Color
- Golden yellow to deep brown with silky chatoyant bands
- Luster
- Silky to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Golden yellow to deep brown with silky chatoyant bands; Luster: Silky to vitreous; Crystal Structure: Trigonal (fibrous); Cleavage: None; Specific Gravity: 2.64–2.71
Formation & geological history
Formed through the hydrothermal alteration of crocidolite (blue asbestos) where silica replaces the asbestos fibers while preserving the fibrous structure. It typically originates in Precambrian iron formations roughly 2.5 to 3 billion years old.
Uses & applications
Predominantly used in jewelry (cabochons, beads), decorative carvings, and as a popular 'protection' stone in metaphysical collecting and lapidary arts.
Geological facts
It is a prime example of a 'pseudomorph,' meaning 'false form.' The chatoyancy (cat's-eye effect) is caused by light reflecting off the preserved mineral fibers. If the iron is replaced by different oxidation states, it can turn into Hawk's Eye (blue) or Bull's Eye (red).
Field identification & locations
Identify by rotating under light to observe the moving golden bands (chatoyancy). Common locations include South Africa (Northern Cape), Western Australia, India, and Namibia. Collectors should look for high contrast between the dark and light gold bands.
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