Moonstone
Mineral #15AB14

Moonstone describes any variety of Feldspar with an adularescent sheen. This "sheen" is caused by light reflecting internally in the Moonstone, from layer inclusions of different Feldspars. Polished Moonstone specimens commonly exhibit chatoyancy, and sometimes displays a strong cat's eye. Different Feldspar varieties produce Moonstone. The most common Moonstone is of the mineral Adularia. The Plagioclase Feldspar Oligoclase also produces famous Moonstone specimens. Rarer forms of Moonstone are from the Plagioclase Feldspars Albite and Labradorite.
Moonstone is a popular gem, and comes in an assortment of colors. It is colorless to light blue, and may also be white, yellow, orange, and reddish.