Adularescence

adularescence \ə-ˌdü -lə-ˈre-sən(t)s\ noun: an optical phenomenon in certain gems in which a milky luster or glow seems to originate below the surface of the stone and appears to move as the stone is turned, giving the impression of moonlight on water

Etymology: From aldularia, a mineral from the Aldula Mountains of Switzerland

Moonstone, so named for its moonlight-on-water optical property, is composed of aldularia crystal.