Cat's Eye (Chrysoberyl)

History and lore

Many gems can show a "cat's eye", a single bright band of light that glides across a domed stone as it is turned, an effect called chatoyancy from the French chat, "cat". Quartz, tourmaline and other stones can display it, but in the gem trade the unqualified name "cat's eye" belongs to chrysoberyl, whose eye is the sharpest and whose colours, honey, greenish yellow and brown, are the most admired. An older name for it is cymophane, "wave-appearing".

Sri Lanka's gem gravels, especially around Ratnapura, have been the classic source for many centuries, with further production from India (Odisha and Kerala), Brazil, Madagascar and Tanzania. Kunz and other collectors of gem lore recorded beliefs across South and South-East Asia that a cat's eye guarded its owner's wealth and protected against poverty and hidden enemies. In late nineteenth-century Britain, as Ceylonese stones reached London in quantity, fine cat's eyes enjoyed a vogue in rings and pins. The rare colour-changing variety of the same mineral is alexandrite, and a few alexandrites show an eye as well.

In the traditions

In the Vedic Navaratna, cat's eye is the gem of Ketu, the south (descending) node of the Moon. Ketu and its partner Rahu are "shadow planets" (chāyā graha): points where the Moon's path crosses the Sun's and eclipses can occur. Puranic myth tells how the demon Svarbhānu slipped among the gods to drink the nectar of immortality at the churning of the ocean and was cut in two by Vishnu's discus; the immortal head became Rahu, the body Ketu. Rahu's gem is hessonite, and the full set, with ruby for the Sun, pearl for the Moon and coral for Mars among them, makes up the nine-gem Navaratna jewel. In Vimśottarī reckoning Ketu rules the lunar mansions Ashwini, Magha and Mula.

Ketu is associated with detachment, spiritual liberation (moksha), sudden events and the karma of past lives, and jyotiṣa practitioners regard its stone as powerful and unpredictable; many traditionally advise a trial period before wearing it permanently. Gem chapters such as the one in Varāhamihira's Bṛhat Saṃhitā (sixth century) discuss vaiḍūrya, but whether that word meant cat's eye, beryl or another stone in early sources is debated; the Greek beryllos probably derives from the same Indian word. Because Ketu is not one of the seven classical planets, this entry gives no Western planet. Some older European month lists collected by Kunz give cat's eye to June.

Meaning and symbolism

The watchful eye is the heart of the stone's symbolism: vigilance, insight and protection, including protection against the evil eye. In the Indian tradition it carries Ketu's double character of loss and liberation. These are the meanings the traditions give; scientific studies have not found that gems or planetary remedies influence fortune or health.

The mineral

Chrysoberyl is a beryllium aluminium oxide with a hardness of 8.5, harder than any common gem except diamond and corundum, and very tough. The eye is produced by great numbers of extremely fine, parallel needles or hollow channels inside the crystal, which scatter light into a single line. Cutters shape the stone as a cabochon with its base parallel to the fibres, so that the eye runs straight across the centre. Lit from one side, a fine stone shows the "milk and honey" effect: one half pale and milky, the other rich yellow.

The most convincing imitation is fibre-optic glass, which shows a honeycomb pattern when viewed from the side; quartz cat's eye is lighter and usually has a duller, fuzzier eye. Some stones are irradiated or heated to improve colour. Cat's eye is durable and can be cleaned with warm soapy water.

Sources and further reading

• Bṛhat Saṃhitā — Varāhamihira, c. 550 CE
• Natural History, Book 37 — Pliny the Elder, c. 77 CE
• The Curious Lore of Precious Stones — George Frederick Kunz, 1913
• Gems: Their Sources, Descriptions and Identification (6th ed.) — Michael O'Donoghue (ed.), 2006
• Gemstones of the World — Walter Schumann, 1977