Moonstone is the commonest type of Feldspar. It has historically been prized for its unique adularescence or schiller effect. The lustrous adularescence effect echoes the milky glow of moonlight, after which it has gained its name.
Moonstones are also known as ‘Adularia’ in reference to Mount Adular, Switzerland, a primary source of moonstone. Other sources of moonstone are found in Burma and Sri Lanka.