metamorphic
Blue Tiger's Eye (Hawk's Eye)
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Blue-gray to blue-green with chatoyancy; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None; Specific gravity: 2.64–2.71
- Hardness
- 6
- Color
- Blue-gray to blue-green with chatoyancy
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Blue-gray to blue-green with chatoyancy; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None; Specific gravity: 2.64–2.71
Formation & geological history
Formed through a pseudomorphic process where silica (quartz) replaces fibrous crocidolite asbestos while maintaining the original fibrous structure. It typically originates in iron formations of the Precambrian age.
Uses & applications
Used primarily in lapidary arts for cabochons, beads, carvings, and jewelry. It is also a popular specimen for crystal collecting and metaphysical practices.
Geological facts
Unlike traditional gold Tiger's Eye, Blue Tiger's Eye (Hawk's Eye) is the original unoxidized form. If it were heated naturally or artificially, the iron would oxidize to turn it golden and brown.
Field identification & locations
Identify by its 'chatoyancy'—a moving silky band of light that appears to glide across the surface as the stone is tilted. It is most commonly sourced from the Northern Cape Province in South Africa and Western Australia.
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