metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Golden-yellow to deep brown with silky chatoyancy; Luster: Silky to glassy; 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 to glassy
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Golden-yellow to deep brown with silky chatoyancy; Luster: Silky to glassy; Crystal structure: Trigonal/Fibrous; Cleavage: None; Specific gravity: 2.64–2.71
Formation & geological history
Formed through the replacement of fibrous crocidolite (blue asbestos) with silica. This process is known as pseudomorphism. As the silica infills the fibrous structure, iron oxide stains the fibers golden-brown. Most deposits are associated with Proterozoic iron formations (approx. 2 billion years old).
Uses & applications
Predominantly used as a gemstone for jewelry (beads, cabochons), ornamental carvings, and 'metaphysical' healing stones. Due to its durability, it is also used in small decorative inlay work.
Geological facts
The shimmering 'cat's eye' effect is called chatoyancy. In Ancient Egypt, it was used to represent the eyes of deities. It is considered a 'pseudomorph' because it maintains the fibrous shape of the original mineral it replaced.
Field identification & locations
Identify by rotating it in light to see the shimmering bands move (chatoyancy). It is commonly found in South Africa (Northern Cape), Australia, and Namibia. In the field, look for banded iron formations with golden fibrous veins.
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