Adularia

[Sarah]

A transparent or translucent variety of common feldspar, ororthoclase, which often shows pearly opalescent reflections; --called by lapidaries moonstone.

[Kit]

[Adult] [diarrhea].

[Britney]

A potassium feldspar that occurs in schists (notably in the Swiss Alps), often with a distinctive opalescence, and is now regarded as a variety of orthoclase.