Tiger’s Eye is a distinctive and widely recognized gemstone, celebrated for its unique visual appeal. Its captivating appearance, characterized by a shimmering play of light, has drawn admiration across cultures for centuries. This popular stone’s intriguing look stems from a specific geological formation process.
Defining Tiger’s Eye
Tiger’s Eye is a form of quartz, primarily composed of silicon dioxide (SiO2). What sets Tiger’s Eye apart is its formation through a process where quartz replaces fibrous amphibole minerals, specifically crocidolite, while largely preserving the original fibrous structure. The resulting stone typically displays golden to reddish-brown colors with a silky luster.
A defining characteristic of Tiger’s Eye is its optical phenomenon known as chatoyancy, often referred to as the “cat’s eye” effect. This effect manifests as a bright band of light that appears to glide across the stone’s surface when it is moved. Chatoyancy occurs due to the reflection and scattering of light by the precisely aligned fibrous inclusions within the quartz. The stone’s hardness measures around 7 on the Mohs scale, indicating its relative durability for various applications.
The fibrous inclusions that cause chatoyancy in Tiger’s Eye are typically altered crocidolite, a type of asbestos. As the crocidolite weathers and changes, it is gradually replaced by quartz and iron oxides, which contribute to the stone’s color.
Geological Origins and Common Applications
The formation of Tiger’s Eye is a geological process involving pseudomorphism, where one mineral replaces another while retaining the original mineral’s shape or fibrous structure. In the case of Tiger’s Eye, quartz replaces the crocidolite fibers, which are initially blue, through silicification. The characteristic golden-brown hues develop as the original blue crocidolite alters to limonite, a hydrated iron (III) oxide, through oxidation. This transformation occurs under specific geological conditions.
Significant deposits of Tiger’s Eye are found globally. South Africa is a prominent source, known for high-quality golden-brown and blue varieties. Other notable locations include Western Australia, India, and parts of the United States. Brazil, Canada, China, and Myanmar also contribute to the global supply.
Tiger’s Eye is widely used in jewelry. It is commonly cut into cabochons to best display its chatoyancy, and also fashioned into beads, carvings, and tumbled stones. These forms are incorporated into rings, necklaces, bracelets, and earrings. Beyond jewelry, Tiger’s Eye is valued as an ornamental and decorative stone. Historically, it has been regarded as a protective stone in various cultures; Roman soldiers wore it for courage, and ancient Egyptians associated it with divine vision and protection.