Cheetah Stone: Tiger's Eye Gems

Tiger's eye forms when quartz slowly replaces fibres of another mineral, crocidolite, inside the rock. The quartz keeps the fibrous structure, and when the stone is cut as a rounded cabochon those fibres catch the light in a moving, silky streak. Gemmologists call the effect chatoyancy. In the bazaar you will often hear it called Cheetah Stone.

The classic colour is golden yellow to warm brown, with stripes that glint as the stone turns. Blue grey material, called hawk's eye, comes from the same process before the iron has oxidised.

Picking a good one

Hold the stone under a single light and roll it gently. A sharp, bright band that moves smoothly is what you want. Dull patches or a blurry sheen lower the value. Even, unbroken stripes look best in a large oval or rectangular cabochon. Watch for colour: red tiger's eye is usually heat-treated golden material, and vivid blues, greens or pinks are almost always dyed. Our listings state what we know about each stone's treatment.

Because it is affordable and bold, tiger's eye is a favourite for large men's rings in silver, often 15 carats or more. It also works well in a simple pendant or a set of beads. Tradition sometimes links it with confidence and courage; that is folklore, and we offer it as such.

At 7 on the hardness scale, tiger's eye is easy to live with. A smooth domed cabochon resists chipping in a bezel or a firm claw setting. Clean it with soap and water, and avoid harsh chemicals, which can dull the polish over time.