18th - Cat's Eye

The rounded cabochon cut can produce a striking visual effect in certain gemstones, creating a straight line reminiscent of a cat's eye due to tiny inclusions that reflect light in a particular way. This effect is similar to the star in a star sapphire, but only

halfway. The chrysoberyl is the rarest gemstone that exhibits this phenomenon, but it can also occur in other gemstones like quartz, sapphire, and ruby.