metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2 with iron oxide inclusions)
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None; Specific gravity: 2.64–2.71.
- Hardness
- 6
- Color
- Golden yellow to deep brown
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Golden yellow to deep brown; Luster: Silky; Crystal structure: Trigonal (fibrous); Cleavage: None; Specific gravity: 2.64–2.71.
Formation & geological history
Formed when quartz replaces parallel fibers of crocidolite (blue asbestos) through a process of pseudomorphism, preserving the fibrous structure. Iron within the mineral oxidizes, creating the golden-brown color.
Uses & applications
Primarily used in jewelry (cabochons, beads, pendants), ornamental carvings, and as a popular gemstone for mineral collectors due to its unique optical properties.
Geological facts
It exhibits chatoyancy, or the 'cat's-eye effect,' which causes light to reflect off the internal parallel fibers, making the specimen appear to shimmer or move as it is turned.
Field identification & locations
Identify in the field by its distinct chatoyancy (moving bands of light) and golden-yellow to brown banding. Common locations include South Africa (Griequaland West), Western Australia, India, and Namibia.
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