metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 7 Mohs; Color: Golden-brown to yellow with chatoyancy; Luster: Silky; Crystal Structure: Trigonal (fibrous texture); Cleavage: None; Specific Gravity: 2.64-2.71
- Hardness
- 7 Mohs
- Color
- Golden-brown to yellow with chatoyancy
- Luster
- Silky
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Physical properties
Hardness: 7 Mohs; Color: Golden-brown to yellow with chatoyancy; Luster: Silky; Crystal Structure: Trigonal (fibrous texture); Cleavage: None; Specific Gravity: 2.64-2.71
Formation & geological history
Formed through a process called pseudomorphism, where silica (quartz) replaces fibrous blue crocidolite asbestos fibers over time, often retaining the original fibrous structure. Most deposits are approximately 2 billion years old.
Uses & applications
Primarily used in jewelry (cabochons, beads), decorative carvings, and as a popular collector's mineral.
Geological facts
The 'cat's-eye' effect is known as chatoyancy. When iron levels are lower, the stone remains blue and is called Hawk's Eye. Roman soldiers once wore it to protect them in battle.
Field identification & locations
Identify in the field by its distinct golden stripes and the moving band of light reflecting off the internal fibers when tilted. Common locations include South Africa (Northern Cape), Australia, and Myanmar.
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