metamorphic
Blue Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5-7.0 (Mohs); Color: Dark blue with gray or black streaks; Luster: Silky; Crystal system: Trigonal/Fibrous; Chatoyancy: Present; SG: 2.64-2.71
- Hardness
- 6
- Color
- Dark blue with gray or black streaks
- Luster
- Silky
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Physical properties
Hardness: 6.5-7.0 (Mohs); Color: Dark blue with gray or black streaks; Luster: Silky; Crystal system: Trigonal/Fibrous; Chatoyancy: Present; SG: 2.64-2.71
Formation & geological history
Formed when quartz replaces fibrous crocidolite (blue asbestos) via a process called pseudomorphism, retaining the parallel fiber structure without the toxic properties of raw asbestos.
Uses & applications
Primarily used in jewelry (cabochons, beads), decorative carvings, and as a popular collection stone for its chatoyant ('cat's eye') effect.
Geological facts
Also known as Hawk's Eye. Unlike the gold version, this variety contains less iron oxide, which allows the original blue/gray color of the crocidolite to remain visible.
Field identification & locations
Identify by its 'shimmer' or chatoyancy when tilted in light. Found commonly in South Africa, Australia, and Namibia. Collectors look for high luster and deep, consistent blue coloration.
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