Tiger's eye is a golden to brown quartz that shows a silky band of light gliding across its surface as the stone moves. That moving band is called chatoyancy, from the French word for cat. The stone forms where quartz grew together with fibers of crocidolite, a blue fibrous mineral. The classic source is the Northern Cape of South Africa, and Western Australia produces a banded relative called Marra Mamba.
How tiger's eye forms
Tiger's eye is a fibrous quartz. It contains bundles of tiny parallel fibers of crocidolite, the fibrous form of the mineral riebeckite, or channels left where those fibers once were. Light reflects off the fibers and produces chatoyancy.
The classic explanation, repeated in many older books, was that quartz replaced crocidolite fiber by fiber while keeping its shape, a process called pseudomorphism. Research published in the early 2000s proposed a different mechanism. In this model, cracks in the rock opened and resealed many times. Each time, quartz and crocidolite grew together in thin bands across the crack. The fibers stand roughly perpendicular to the vein walls. Either way, the result is quartz with an aligned fibrous structure.
The golden color comes from iron. Where the crocidolite has altered and oxidized to iron oxides such as goethite and limonite, the stone turns golden yellow to brown. Where the crocidolite stays fresh, it keeps a blue-gray color, and the stone is called hawk's eye.
Hawk's eye and tiger iron
Hawk's eye, also called falcon's eye, is the blue to blue-green form. It forms in the same deposits and often appears in the same piece as tiger's eye, with golden and blue bands side by side.
Tiger iron is a banded rock made of layers of tiger's eye, red jasper and black hematite. It comes from the iron-rich rocks of Western Australia. The red and black layers come from the jasper and iron oxides. Marra Mamba stone is a related banded material from the Hamersley Range in the Pilbara, Western Australia. It shows tiger's eye in gold, red and green with dark bands and is prized by collectors.
Sources
South Africa's Northern Cape province, around Prieska and Griquatown in the region historically called Griqualand West, has been the main source of tiger's eye and hawk's eye. The stone occurs in banded iron formations, very old layered rocks rich in iron and silica. Western Australia's banded iron formations supply tiger iron and Marra Mamba. Namibia, India, China, Brazil, Myanmar and the United States also produce tiger's eye.
Chatoyancy and cutting
Chatoyancy appears only when a stone is cut correctly. Cutters shape tiger's eye as a cabochon with its base parallel to the length of the fibers. Light then reflects from the fibers as a narrow line that runs across them. Turning the stone moves the line. Flat slabs and beads show a rolling, silky shimmer as light moves across the bands.
The same effect appears in cat's eye chrysoberyl, which is far rarer and sharper. The chrysoberyl page compares the two. The gemstone optics page explains chatoyancy and other light effects. Tiger's eye is also carved into figures, bowls, spheres and cameos, and is cut into beads for bracelets.
Treatments
Tiger's eye is often treated, and most treatments are stable.
- Heating turns golden tiger's eye red to red-brown by changing the iron oxides. The trade sells the result as red tiger's eye. Natural red tiger's eye also exists but is less common.
- Acid bleaching lightens the color to a pale honey.
- Dyeing produces bright colors such as red, green, blue and pink.
Sellers should disclose these treatments. The gemstone treatments page covers heating and dyeing in more detail.
Judging quality
Good tiger's eye shows strong, even chatoyancy, rich golden or mixed colors and a high, smooth polish. Stones with sharp, bright bands and a clear moving line are valued above dull or patchy material. Marra Mamba commands higher prices because of its limited supply.
Imitations include glass with fiber optics, which shows a regular grid of fibers under magnification. Fiber-optic glass, sold as cat's eye glass, gives a very sharp band and often shows a honeycomb pattern from the side.
Cutting safety
Tiger's eye contains crocidolite, a form of asbestos, though the fibers are encased in quartz or replaced by it. Lapidaries cut and polish it wet and wear a dust mask to avoid inhaling dust. Finished stones do not release fibers in normal wear.
Durability and care
Tiger's eye has a hardness of 6.5 to 7 and good toughness because of its fibrous structure. It works well in rings, bracelets and pendants. Clean it with warm soapy water and a soft cloth. Avoid harsh chemicals and long soaks, which can affect dyed stones, and avoid sudden temperature changes. Ultrasonic cleaning is usually safe for untreated stones. The guide to cleaning jewelry safely has general advice.
Tradition and folklore
Roman soldiers are often said to have carried tiger's eye for protection, a story repeated widely in modern gem books. Tiger's eye became common in European jewelry after large South African deposits reached the market in the late 19th century. These are cultural beliefs, and the gemstone meanings and folklore page covers more of them.
Frequently asked questions
What is the difference between tiger's eye and hawk's eye?
Both are fibrous quartz with crocidolite. Tiger's eye is golden because the fibers have oxidized to iron oxides. Hawk's eye is blue-gray because the fibers have not.
Is red tiger's eye natural?
Some is, but most red tiger's eye has been heated, which turns golden tiger's eye red.
Is tiger's eye a birthstone?
No. Tiger's eye is not on the standard modern birthstone list. The birthstones by month page shows which gems are.
Why does tiger's eye shimmer?
Parallel fibers inside the stone reflect light in a narrow band. When the stone moves, the band moves too.