Tiger's eye is golden-brown quartz with a silky band of light that sweeps across the stone as it moves, an effect called chatoyancy. It forms when quartz grows through parallel fibres of blue crocidolite that iron then stains gold, preserving the fibrous structure that bends light so beautifully. Roman soldiers reportedly carried it into battle. The world's main source is the Northern Cape of South Africa, with more from Western Australia. Heating natural tiger's eye produces the red version sold as red tiger's eye, a straightforward, disclosed treatment.
With a hardness of 6.5 to 7 and a tough fibrous build, tiger's eye is an easy stone for daily rings, beads, cufflinks and pendants. It must be cut as cabochons or polished shapes with the fibres aligned, because that rolling eye of light is the whole show. A well-cut stone winks at you from across the room. Care is simple: warm, soapy water and a soft brush. Fibre-optic glass imitations exist but look garishly bright and too perfect next to the real thing.
Hawk's eye is the unoxidised grey-blue version, pietersite the storm-patterned one, and tiger iron the banded rock that includes tiger's eye.
