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 and a an 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.
Moonstone is the most well known variety of orthoclase feldspar. It characteristically exhibits a milky floating blue light known as adularescence or the schiller effect. This lovely sheen is due to a combination of orthoclase and albite arranged in layers. Light reflected from the layers if they are not too thick is responsible for the unusual optical properties. 
