Moonstone Cats-eye = Moonstone is characterised by an enchanting play of light. It owes its name to the Blue Sheen which looks different when the stone is turned and is known as 'adularescence'. - Caused by the lamellar inner construction of the gemstone. Incident light rays are refracted and scattered in the stone. This way, a unique light effect is created which makes the moonstone so distinctive.

Sri Lanka is the main source country of the Blue-sheen moonstone - the most attractive type. Some Moonstones display a single ray like a chatoyant effect and are called Cats-eyes which are rare and much sought after by Collectors.