Nope, tone: Cat's-eye or cymophane is also much sought after, on account of the luminous line that bisects it from top to bottom and moves from side to side as the stone is turned. Several other gems also produce cat's-eyes, but none shows a line with such delicate yet sharp silky splendor as chrysoberyl. It is caused by extremely fine hollow channels traversing the stone at right angles to the line. In most other gemstones the 'eye' caused by solid fibrous crystals and is therefore coarser and more diffuse. Accurate cutting is required to place the line exactly in the middle of the stone.
Cat'-eye come mainly from Ceylon's gem gravels and, unlike alexandrite, they have been much prized for thousands of years. The stones are simulated most closely by yellow quartz cat's-eyes but all applicable tests will clearly distinguish between the two gems. No synthetic chrysoberyl cat's-eyes are marked.