Moonstone

Moonstones are an opaque, white feldspar gem polished to a blueish sheen. Old legends say that the sight of a moonstone would cause a lycanthrope to revert to his animal form. While this is not true (in fact, many lycanthropes wear moonstones), devices which affect lycanthropes often use moonstones in their construction and/or decoration. They are considered sacred to the worshipers of the deity Selûne. Moonstones are also used as material components in spell casting. A typical specimen has a base value of 50gp.