ADULARIA
Etymology
Named for the type locality at Adular, Switzerland.
Noun
adularia (plural adularias)
A variety of orthoclase feldspar found as colorless to white prismatic crystals in cavities in metamorphic rocks. Some specimens reflect a bluish sheen along crystal faces. This phenomenon is called adularescence, and adularia with this property is called moonstone. (See sanidine).
Source: Wiktionary
Ad`u*la"ri*a, n. Etym: [From Adula, a mountain peak in Switzerland,
where fine specimens are found.] (Min.)
Definition: A transparent or translucent variety of common feldspar, or
orthoclase, which often shows pearly opalescent reflections; --
called by lapidaries moonstone.
Source: Webster’s Unabridged Dictionary 1913 Edition