adularia

/AE1 D AH0 L AA1 R IY0 AH0/
noun
  1. 1

    (mineralogy) 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).