Tiger eye is a popular gemstone, recognized for its distinctive optical effect known as chatoyancy, which creates a shimmering band of light across its surface. This unique characteristic often resembles the slit eye of a feline predator. While golden-brown tiger eye is widely known, a red variation also exists. A common question arises regarding this red form: is red tiger eye naturally occurring or is it treated to achieve its vibrant hue?
The Origin of Tiger Eye
Tiger eye belongs to the quartz mineral family, primarily composed of silicon dioxide. Its formation begins with crocidolite, a fibrous blue asbestos mineral. Through a geological process called pseudomorphism, quartz gradually replaces the crocidolite fibers. This replacement preserves the original fibrous structure of the crocidolite.
The fibrous arrangement within the quartz is responsible for the stone’s characteristic chatoyancy, as light reflects off these parallel inclusions. The typical golden-brown color of tiger eye results from the presence of iron oxides introduced during this complex mineral transformation.
How Red Tiger Eye Gets Its Color
The reddish color found in red tiger eye primarily stems from the oxidation of iron within the stone. While rare, this oxidation can occur naturally, often triggered by exposure to natural heat sources deep within the Earth. Heat-related geologic processes can transform iron compounds, causing the color change.
Despite some natural occurrences, the majority of red tiger eye available on the market achieves its color through gentle heat treatment of standard golden-brown tiger eye. The heat converts hydrated iron oxides, which typically give the stone a yellow or brown color, into anhydrous iron oxides that exhibit a red hue. Temperatures used for this treatment vary, commonly around 400°F (approximately 200°C), though some methods might involve higher temperatures to fully dehydrate the iron compounds.
Identifying Red Tiger Eye
Naturally occurring red tiger eye is exceptionally rare and commands a higher price. These natural stones might display more subtle or uneven coloration and could contain minor inclusions.
Conversely, heat-treated red tiger eye typically presents a more uniform and vibrant red color. This consistent intensity often signals human intervention, though the treatment is widely accepted within the gem industry. Heat treatment is a stable enhancement that does not diminish the stone’s inherent properties or its characteristic chatoyancy.