Moonstone is a variety of feldspar known as Adularia, a potassium aluminosilicate which can be found in the European Alps near the Adula Group - hence the name 'adularia'.
In their uncut state moonstones are rather unremarkable and suggest little of their subtle charm. It isn't until they have been cut and polished, usually as beads or cabochons that the attractive nature emerges.
The milky shimmer of light and colours within the stone is referred to as 'adularisation'. The cause of it is the lamellar inner construction of the gemstone. Incident light rays are refracted within the stone. Small light catching flecks are called schiller.
Prices of Moonstone can vary from the mundane to the ridiculous. The more transparent and more colourful samples are very, very expensive indeed. We are picky about our Moonstone and have a very good source of supply.