Moonstone is an opalescent stone that come in a number of colors from translucent white to browns and grays.  The milky white ones with a rainbow sheen are called rainbow moonstones.  It is one of the birthstones for June.

Folklore and healing properties:

The ancient Romans believed moonstone was actually formed by moonlight.  In India, it's a sacred stone.  Some Asians believe there is a living spirit in the stone. It was believed by some that holding a moonstone in your mouth during a full moon would reveal the future.   It enhances prophetic abilities.  It is believed to bring good luck and enhance passion and balance.  It is supposed to protect women and children.  Moonstone strengthens intuition and psychic abilities.  A moonstone placed under the pillow is an aid to prophetic dreams. It is the official gemstone of Florida.

It is supposed to aid digestion and help prevent epilepsy.  It is also said to cure headaches and nose bleeds.  It is reputed to reduce high blood pressure.

Moonstone is a fragile gem that must be handled with care.  Clean with a soft polishing cloth and a bit of olive oil.