metamorphic
Tiger's Eye
Pseudomorph of Quartz after Crocidolite (SiO2)
Hardness: 7 (Mohs), Color: Golden brown to yellowish brown with chatoyant bands, Luster: Silky to vitreous (when polished), Crystal Structure: Trigonal (fibrous), Cleavage: None, Specific Gravity: 2.64-2.71
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Physical properties
Hardness: 7 (Mohs), Color: Golden brown to yellowish brown with chatoyant bands, Luster: Silky to vitreous (when polished), Crystal Structure: Trigonal (fibrous), Cleavage: None, Specific Gravity: 2.64-2.71
Formation & geological history
Formed when fibrous blue crocidolite (asbestos) is replaced by silica (Quartz) through a process of pseudomorphism while retaining the fibrous structure. Often found in iron-rich metamorphic rocks associated with banded iron formations.
Uses & applications
Extensively used in jewelry (cabochons, beads), decorative carvings, feng shui, and as a popular collectible for gemstone enthusiasts.
Geological facts
The chatoyancy (cat's eye effect) is caused by the reflection of light off the parallel mineral fibers within the stone. If it is heated, it turns red and is called Bull's Eye.
Field identification & locations
Identified by its distinctive gold and brown bands and silky chatoyancy. It is primarily found in South Africa (Northern Cape Province) and Australia. Small specimens can be identified in the field by their weight and luster under sunlight.
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