metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 (Mohs); Color: Golden yellow to deep brown with distinct banding; Luster: Silky; Crystal structure: Trigonal (fibrous habit); Cleavage: None; Specific gravity: 2.64–2.71.
- Hardness
- 6
- Color
- Golden yellow to deep brown with distinct banding
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs); Color: Golden yellow to deep brown with distinct banding; Luster: Silky; Crystal structure: Trigonal (fibrous habit); Cleavage: None; Specific gravity: 2.64–2.71.
Formation & geological history
Formed through a process called pseudomorphism, where silica-rich fluids replace the fibrous mineral crocidolite (blue asbestos) while retaining its fibrous structure. This results in the characteristic chatoyancy (cat's eye effect). Most deposits are millions of years old, found primarily in folded iron formations.
Uses & applications
Commonly used in lapidary work for cabochons, beads, and carvings. It is popular in jewelry (rings, pendants) and widely collected by mineral enthusiasts for its optical properties. Also used for ornamental carvings like figurines.
Geological facts
The 'shimmer' seen in Tiger's Eye is known as chatoyancy. When the fibers are replaced by quartz but the iron from the crocidolite doesn't oxidize fully, the stone remains blue and is known as Hawk's Eye. If the stone is heat-treated, it turns red and is called Bull's Eye.
Field identification & locations
Identify in the field by its distinct parallel yellow/brown bands and chatoyant 'cat's eye' effect when rotated under light. Major locations include South Africa (Northern Cape), Western Australia, India, and Namibia. Collectors should look for sharp, clean bands and high luster.
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