metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Golden-yellow to brown with silky banding; Luster: Silky; Crystal structure: Trigonal/Fibrous; Specific Gravity: 2.64–2.71; Notable chatoyancy effect.
- Hardness
- 6
- Color
- Golden-yellow to brown with silky banding
- Luster
- Silky
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Golden-yellow to brown with silky banding; Luster: Silky; Crystal structure: Trigonal/Fibrous; Specific Gravity: 2.64–2.71; Notable chatoyancy effect.
Formation & geological history
Formed when quartz replaces the mineral crocidolite (blue asbestos) through a process of hydrothermal alteration, retaining the fibrous structure of the original mineral. This pseudomorphism occurs in metamorphic environments.
Uses & applications
Primarily used as a semi-precious gemstone in jewelry (rings, pendants, beads), ornamental carvings, and by crystal collectors for its aesthetic and perceived metaphysical properties.
Geological facts
The unique 'cat's eye' effect (chatoyancy) is caused by the reflection of light off the fibrous structure of the quartz. When the fibers are oriented vertically, the stone appears to 'blink' as it is turned.
Field identification & locations
Identify in the field by its distinct golden-brown color bands and the way light moves across the surface (chatoyancy). It is commonly found in Griqualand West, South Africa, and parts of Western Australia.
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