metamorphic
Blue Tiger's Eye (Hawk's Eye)
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5-7.0 (Mohs scale); Color: Blue-gray to blue-green with chatoyancy; Luster: Silky; Crystal structure: Trigonal; No cleavage; 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: 6.5-7.0 (Mohs scale); Color: Blue-gray to blue-green with chatoyancy; Luster: Silky; Crystal structure: Trigonal; No cleavage; Specific gravity: 2.64-2.71
Formation & geological history
Formed through a process called pseudomorphism, where fibrous crocidolite asbestos is progressively replaced by silica (quartz). Unlike golden Tiger's Eye, the blue variety retains more of the original iron content and has not been subjected to the same oxidation levels during its geological formation.
Uses & applications
Predominantly used for lapidary purposes, including jewelry (cabochons, beads), decorative carvings, and collection specimens. It is highly valued in the 'metaphysical' community.
Geological facts
Also known as Falcon's Eye, it is considered a rarer natural phase than the oxidized golden-brown Tiger's Eye. The optical effect, known as chatoyancy, is caused by the reflection of light off the parallel mineral fibers trapped within the quartz.
Field identification & locations
Identify in the field by its distinct 'cat's eye' silky luster that moves as the stone is rotated under light. It is commonly found in South Africa and Australia, often associated with banded iron formations.
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