Moonstone and Sapphire Ring. Moonstone is so-named for its luminous appearance, enhanced by a unique, ghostly sheen visible from certain angles. This ghostly sheen, which can be white, blue or a light yellow, is known as ‘adularescence’, and is caused by light reflecting through the stone’s intricately layered crystal structure. The stone is almost always cut as a cabochon to show off this effect to its fullest, and this example is no exception. Unusually, it is set within a border of circular-cut sapphires, the yellow gold mount bringing out the deeper blues of the sapphires and more subtle bluish hues of its central stone. An interesting and beautiful cluster ring, perfect as a standalone dress ring.