Tiger's Eye: Is It Safe, and How to Judge a Bracelet

Tiger's eye is quartz with fine fibres running through it in one direction. Its golden brown comes from iron in those fibres, which oxidised as water moved through the rock. Turn a bead under a lamp and a bright line slides across it. That line is the cat's-eye band, and it is the first thing to look at in a tiger's eye bracelet.

The main recorded source is the Northern Cape of South Africa, around Prieska, and tiger's eye is also recorded in Western Australia. At Mohs 6.5–7 it wears like any quartz, and it takes a high polish with a silky lustre.

What is tiger's eye?

Tiger's eye is quartz, SiO₂, with fine aligned fibres derived from crocidolite, a blue amphibole. How it formed is still debated. For the South African specimens they examined, Heaney and Fisher proposed that quartz and crocidolite fibres grew together as cracks repeatedly opened and sealed. They published this crack-and-seal interpretation in Geology in 2003. The older account, dating back to 1873, has quartz replacing crocidolite while keeping the shape of its fibres. In 2004, geologists working from South African field evidence read it as crocidolite veins that were first silicified and then partly oxidised.

Crocidolite is blue. The gold came later, when water moving through the rock oxidised part of the iron in the fibres to iron oxides and hydroxides, the same brown and gold family that colours ochre. Where oxidation went further, the stone turned golden brown. Where it went less far, the fibres kept their blue, and that material is sold as hawk's eye. Yellow and blue areas occur together in material documented near Prieska, South Africa.

The lighter and darker stripes that cross a golden bead are part of what makes tiger's eye easy to recognise at a glance. In the crack-and-seal reading they are successive growth layers. How they sit against the band varies with the cut and with the direction of the fibres inside.

Where does the cat's-eye band come from?

From the fibres. Thousands of them lie side by side, and light reflecting off them lines up into one bright band that runs across the fibre direction. Turn the bead and the band moves, because the angle between your eye, the lamp and the fibres has changed. The effect is called chatoyancy, from the French for cat's eye.

Aligned mineral fibres produce the moving band of light. Turn the strand under one lamp to see how the band appears on each bead.

Each bead is cut on its own and then strung, so the fibres in one bead point a slightly different way from those in the next. Turn the bracelet under one lamp and the bands do not move in step: some beads light up together, some a moment later, and a few show a soft sheen in place of a line. A strand of separately cut beads usually does this.

How do you judge a tiger's eye bracelet?

Look at the band first and the colour second. Crystal 4T™ reads tiger's eye as an optical-effect stone, so the band is scored under Transparency and the colour under Tone. Both are read by eye at wearing distance, about 40 cm, under daylight-balanced light. BE. only puts about the top 20% of inspected material into the studio, and then scores each reading.

Transparency on an opaque stone means surface light. A strand that reads Exceptional shows the band on every bead when you hold it at wearing distance, while at Standard most beads show it only when you look closely. To see this for yourself, hold the bracelet near a window and turn it slowly. On a strong strand, bead after bead catches the light.

Tone has two layers. Within each bead, the golden brown should be full and warm, neither washed out nor muddy, and the band itself should read as clean gold. Across the strand, the colour should hold from one bead to the next. At Exceptional, no difference between beads is visible at wearing distance. The natural stripes inside each bead do not count against it, since stripes are a normal part of tiger's eye.

Texture is read the same way for every stone BE. works with: polish, drill holes, roundness and diameter.

Is tiger's eye treated?

The treatments recorded for tiger's eye include heating, bleaching and dyeing.

1. Red tiger's eye can be produced by heating. Heating turns golden-brown material red, and it is a treatment that should be stated. Red is also sold as bull's eye, a trade name with no definition of its own.
2. Colour can be lightened by bleaching. GIA lists bleaching as a tiger's eye treatment and notes that it is difficult to detect, so a golden colour on its own does not show whether a stone has been treated.
3. Tiger's eye can be dyed. Colour alone does not establish treatment status.

A stone enters BE. only if it is untreated, so bleached and dyed material never goes into a BE. strand. Heated material does not enter BE. For tiger's eye, BE. carries golden material only. On the Record, the Treatment line gives the treatment status. The crystal treatment disclosure chart lists the common treatments stone by stone.

How can you tell real tiger's eye from an imitation?

The usual imitation is fibre-optic glass sold as "cat's eye". It can be made in many colours and can show an unusually sharp band. Look at a glass bead from the side. The cut fibre ends can show a fine honeycomb pattern.

Real tiger's eye looks different once it is in your hand. The band rolls across golden and brown stripes, the stripes change from bead to bead, and the band on each bead sits at its own angle. A colour tiger's eye never has in nature, such as pink or bright green, points to dye or glass. The guide to real and fake crystals covers glass imitations of other stones.

Tiger's eye in historical records

Robert H. Jones recorded the name “Tiger-eye” in his 1888 book Asbestos: Its Production and Use. Writing about material from Griqualand in South Africa, he noted that it was called tiger-eye in the United States. He presumed the name referred to its tawny, streaked appearance. He offered this as his own explanation; who first chose the name remains unknown.

A British museum guide published in 1912 distinguished golden tiger-eye from blue hawk's-eye. The Metropolitan Museum of Art also catalogues a nineteenth-century Japanese inrō with an ojime identified as a tiger's-eye bead. The record preserves a particular use of the stone in a dated object.

References

• Heaney, P.J. & Fisher, D.M. (2003). "New interpretation of the origin of tiger's-eye." Geology 31(4): 323–326.
• Tiger's eye: composition, intergrowth with altered amphibole, trade variants and treatments
• Jin et al. (2025). "Structures Behind the Spectacle." Gems & Gemology, Summer 2025.
• GIA: An Introduction to Gem Treatments
• White, N.W., Chetty, R. & Bateman, E.D. (1991). "Silicosis among gemstone workers in South Africa: tiger's-eye pneumoconiosis." American Journal of Industrial Medicine.