Tiger eye is a captivating gemstone known for its distinctive optical phenomenon, chatoyancy, often called the “cat’s eye effect.” This unique characteristic creates a silky, luminous band of light that appears to glide across its surface. Understanding its natural properties helps explore the origins of its various color forms, especially the popular pink variety.
Understanding Tiger Eye
Tiger eye is a metamorphic rock primarily composed of silicon dioxide. Its characteristic golden-brown color and chatoyancy arise from a geological process. Originally, fibrous minerals like crocidolite (a type of asbestos) form within the host rock. Over long periods, these fibers are gradually replaced by quartz and iron oxides, mainly limonite, through pseudomorphism. This replacement retains the parallel fibrous structure, reflecting light to create the shimmering “eye” effect. Natural tiger eye typically exhibits colors from golden-yellow to golden-brown, and sometimes blue-gray (hawk’s eye). Reddish-brown variations, often called ox blood or bull’s eye, can also occur naturally from exposure to heat within the earth.
The Truth About Pink Tiger Eye
Naturally occurring pink tiger eye is extremely rare, almost non-existent in the market. Most pink tiger eye available today results from treatments applied to natural golden-brown tiger eye. While golden-brown tiger eye is common, and reddish-brown variations can occur naturally, pink hues are almost always man-made. This distinction is important for consumers seeking authentic, untreated gemstones.
Methods of Color Enhancement
The pink color in most pink tiger eye is typically achieved through color enhancement, primarily heat treatment. When golden-brown tiger eye is subjected to controlled heating, often around 400°C (750°F), the limonite (hydrated iron oxide) within the stone transforms into hematite (anhydrous iron oxide). This chemical change alters the iron content, shifting the stone’s color from golden-brown to reddish or pinkish hues. While heat treatment is the main method, some pink tiger eye may also involve dyeing. Dyeing introduces artificial color, identifiable by its uniformity or intensity.
How to Identify Authenticity
Identifying whether pink tiger eye is natural or treated involves careful observation. Untreated tiger eye typically shows golden-yellow, brown, or blue-gray shades, with a distinct, moving chatoyancy band. Treated pink tiger eye may display an overly vibrant, uniform, or unnaturally bright color. Examining the stone for dye concentrations, especially in cracks or fissures, can indicate artificial coloring.
Real tiger eye is relatively hard, rating around 7 on the Mohs scale, meaning it can scratch glass. If the color rubs off with acetone, it suggests the stone has been dyed. While these tests provide clues, definitive identification often requires professional gemological testing.