Moonstone is a sodium potassium aluminium silicate of the feldspar group that displays a pearly and opalescent schiller. An alternative name is hecatolite. Moonstone has been used in jewelry for millennia, including ancient civilizations. The Romans admired moonstone, as they believed it was born from solidified rays of the Moon. In more recent history, moonstone became popular during the Art Nouveau period; French goldsmith René Lalique and many others created a large quantity of jewelry using this stone.