Which of the following is widely recognized as the most valuable chatoyant gem?

The most valuable chatoyant gem is cat's-eye chrysoberyl. Chatoyancy, a phenomenon that results in a unique appearance resembling a cat's eye, is particularly well-displayed in this gemstone. Cat's-eye chrysoberyl exhibits an exceptional interplay of light due to its fibrous inclusions, which create a striking, reflected band of light across its surface. This optical effect enhances the gem's allure and contributes to its higher valuation in comparison to other stones.

While emeralds, alexandrites, and tourmalines are valuable in their own right and may possess their own unique characteristics and color variations, they do not exhibit chatoyancy in the same pronounced manner as cat's-eye chrysoberyl. The rarity and quality of chatoyant chrysoberyl, especially with a well-defined eye, further elevate its status among collectors and gem enthusiasts. Therefore, the specific characteristics of cat's-eye chrysoberyl position it as the most valuable chatoyant gem in the world of colored stones.