There is a certain fascination about having your gemstone not only looking back at you, but giving you the occasional wink. For that reason, the cat’s-eye is a favorite among gemologists and gem merchants.
The cat’s-eye effect is a lighting phenomenon that gives certain gemstones the appearance of a cat’s narrowing pupil—hence the name. It’s a bright, thin line of light that stretches from one end to the other of a cabochon-cut gemstone. The bright line is created by the reflection of light off long, thin inclusions. Inside the gem, the reflected light is projected upwards and across the dome of the cab. The phenomenon is also known as chatoyancy. (“Chat” is French for “cat.”)
There are cat’s-eyes of many gem species, including tourmaline, quartz, spinel, diopside, actinolite, apatite, scapolite, sillimanite, feldspar (“cat’s-eye moonstone”), and even beryl (especially notable is the emerald cat’s-eye.) Tiger’s-eye quartz, also considered a cat’s-eye, is one in which the fibrous inclusions are themselves curved and wavy, and therefore create the cat’s-eye without the need to cabochon the gem.
However, when you simply say the name “cat’s-eye,” it is assumed that you mean the most prized of all cat’s-eyes, the chrysoberyl cat’s-eye. Of all the natural gem cat’s-eyes, this one can have the brightest and sharpest of all eyes. It’s among the retail jeweler’s top choice to wear, since it has great durability, great presence, and can spark a good conversation with a customer about phenomenal gemstones.
History. According to the literature, cat’s-eyes have a long history, dating back at least to first-century Rome. Sri Lanka and India are the two most likely sources for chrysoberyl cat’s-eye from this period. Seemingly forgotten for many centuries, the gem suddenly became in great demand just after the British Duke of Connaught (1850-1942), third son of Queen Victoria, gave a cat’s-eye engagement ring to Princess Louise Margaret of Prussia in 1879.
Today, most cat’s-eyes come from those same regions of eastern India and Sri Lanka, as well as from Brazil. Other notable localities include Burma, China, and Madagascar.
Not only beautiful in appearance, cat’s-eyes are said to have mystical powers: They supposedly are able to protect the wearer from evil spirits as well as disease and poverty. Pressing the cat’s-eye against one’s forehead gives the wearer foresight, a clear vision of the future. One of the largest and more famous cat’s-eyes is found in the Smithsonian’s gem collection. The semi-transparent golden yellow Sri Lankan “Maharani” (named after a type of Burmese cat) weighs just over 58 cts.
Color. In general, colors for chrysoberyl are in the yellow and green to brown ranges. Cat’s-eyes tend towards combinations of colors, such as greenish-yellow, brownish-yellow, yellowish-green, and yellowish-brown, rather than any pure color of green, yellow, or brown.
Quality and value. Pay close attention to three important quality features: color, transparency, and, most importantly, the eye itself. When looking for top-quality chrysoberyl cat’s-eye, choose a stone that has the color and transparency of honey, a yellow- (“golden-“) brown. The more the color tends toward straight yellow, green, or brown, the less valuable the stone becomes.
Inclusions necessary for the cat’s-eye effect can reduce the gem’s transparency. Being both transparent, or at least semi-transparent, and having a nice eye, is preferred, and more rare. Translucent to opaque cat’s-eyes are much more common.
To show a cat’s-eye effect, the gem has to have an abundance of straight fibers or tube-like cavities/channels. The gem must be fashioned in a dome, in cabochon, and the inclusions must be oriented parallel to the base, and perpendicular to the length. (A faceted stone with these inclusions will exhibit a sheen across facet surfaces.)
Three things to note about the actual cat’s-eye itself: It must be razor-sharp, it must be complete, and it must be straight. To check for these qualities, you’ll need a strong single light source. Under this light, the eye should be perfectly straight, with no breaks from one end of the cabochon to the other. Two light sources will cause two cat’s-eyes, and diffuse lights will create diffuse cat’s-eyes.
The sharpness of the eye comes not only from the light source, but more importantly from having fine and evenly spaced inclusions across the width and length of the stone, as well as the stone being polished into a nicely shaped dome. In order for the eye to be straight down the length and top of the cabochon, the gem cutter must place the inclusions exactly perpendicular to the ends and parallel to the base of the oval. One should move the gem, or light source, back and forth to see how well the eye moves across the top of the gem. A well- proportioned gem with a well-defined eye will show the band of light moving effortlessly from one side to the other, always remaining straight and complete.
To see the eye wink, use two strong direct light sources and rotate the stone. There are two points when the lights are both shining down the length of the gem, at 12 and 6 o’clock, and the eye will shine bright and straight. As the stone rotates and the lights now fall on opposite sides of the length’s apex, you will see two bright lines, two eyes, one from each light source. The eye is said to be opening. If the cabochon is cut properly, you will have a good-sized opening of the eye when the lights are at 3 and 9 o’clock.
You will find high domes on gems that do not have enough inclusions or fine-enough inclusions. The high dome helps to concentrate less reflected light. The high dome may give the appearance of a nice cat’s-eye from the top, but it will fail to move across the top when rocking the gem back and forth. Also, there will be a very poor visual of the eye opening and closing as the stone is rotated underneath two light sources. The high dome itself doesn’t add to the beauty of the gem’s design, and it adds unnecessary weight to the gem.
Another feature of a good-quality cat’s-eye is its “milk and honey” effect. To achieve this, you first need saturation of good color. You also need good transparency, and a light source that enters the stone from the side, perpendicular to the cat’s-eye. The reflection off the inclusions gives the stone a dark honey color on the side of the light source, and a milky lighter color on the side away from the light, with the eye’s white line dividing the two colors.
Price. According to The Guide , fine quality cat’s-eyes in 5-10 cts. can range in price from $2,200/ct. to $3,000/ct. Extra-fine qualities can reach up to $5,000/ct. Gems of more than 10 cts. are rare and prices are negotiable.
Enhancements. As far as we know, there are currently no enhancements for cat’s-eye chrysoberyl. However, in the late 1990s, there were a number of very dark brown cat’s-eyes that were found to have been exposed to very high levels of radiation. All dark brown cat’s-eyes should therefore be checked for residual harmful radiation.
Bench care and cleaning. Chrysoberyl cat’s-eyes are very durable, which is why you will see them mounted in rings for both men and women. Chrysoberyl has a hardness of 8.5 on the Mohs scale, so they can wear fairly well without getting scratched. They are also tough, which is why they can take a pretty good hit and still not get damaged. Ultrasonic and steam cleaning should be just fine for the chrysoberyl cat’s-eye.