The Catseyes Gemstone,Its Chatoyancy Effect & As Jewellery

Posted by slang on April 30, 2007

This gemstone is named after the cat’s-eye appearance of the single sharp, vertical line displayed when light is reflected off its surface.

The name “cat’s-eye” normally refers to cat’s-eye chrysoberyl. In the Ancient Rome, the Romans were familiar with cat’s-eye chrysoberyl by the first century.In the East it was believed that pressing a cat’s-eye on the forehead between the eyes would endow a person with clearness of foresight. 

In Sri Lanka, the original historical source of cat’s-eye chrysoberyl, it was believed to offer protection from demons.

The most desirable cat’s-eye chrysoberyls show a distinct band of light centered on the cabochon’s surface. As the light source moves, this band also moves from left to right, and the coloration on either side of the band changes. Most highly prized are those that show a honey color on the side closer to the light source and a milky translucence on the far side. This cat’s-eye effect is called “chatoyancy,” derived from chat, the French word for “cat.” Chatoyancy is caused by numerous parallel, needle-like inclusions within the stone. Light reflected off these inclusions is focused by the cabochon’s curved surface, causing the chatoyant band to appear. If the cabochon surface is too high, a sharp band still appears, but it will not move back and forth. A low cabochon surface makes the band wavy and indistinct. On poorly cut stones, the band may be off-center or run diagonally across the stone.Cat’s-eye is a variety of the mineral chrysoberyl, as is alexandrite, which changes color between incandescent and fluorescent lighting. The rare cat’s-eye alexandrite exhibits both effects simultaneously.

The ideal choice for a cat’s-eye chrysoberyl is one that exhibits :-

• distinct chatoyancy and
• a well-balanced change in its honey-colored and milky portions as it moves,
• and has a good overall shape and form.

In reality, however, such a stone rarely exists. The optimum size for a cat’s-eye used as the main stone in a ring is 7 to 8 millimeters (about .25 to .33 inch), and a weight of over two carats. Assuming that a pleasing overall appearance is the absolute minimum requirement, it is realistic to choose a stone with emphasis on either the appearance of the chatoyancy, or the stone’s color.

When buying loose stones, it is especially important to not select a stone with a base that is too deep. It is difficult to set a deep stone in jewelry, and odds are that such a gemstone would end up not being used at all.The value of a three-carat-size cat’s-eye chrysoberyl of jewelry quality is approximately US $5,000 for the stone alone.(Year 2001: auction houses of Christie and Sotheby)

At the auction houses of Christie’s and Sotheby’s, men’s rings set with cat’s-eye chrysoberyls exceeding five carats occasionally come up for sale. Although cat’s-eye chrysoberyl is a gemstone favored by men in the United States because of its exceptional durability, in Japan, relatively small cat’s-eyes weighing two to three carats are often fashioned into and sold as women’s rings.

The current major sources of cat’s-eye chrysoberyl are Sri Lanka,Tanzania, Brazil, and India.