Glossary of Terms
Optical effect exhibited on certain minerals and gemstones where they display a billowy, ghost-like reflection with a bluish-whitish color emanating from the surface. This effect is caused by structural anomalies or a build up of water in the mineral. Opal and Moonstone are the most well-known adularescent minerals. The name is derived from the feldspar variety of Adularia, of which Moonstone belongs to.