The description in the Sundance Catalog says:
Moonstone is said to balance yin and yang energy. It is one of the birthstones for June and for the zodiac sign of Cancer. In India, it is a sacred stone, believed to bring good luck. Legend has made moonstone, said to arouse tender passion, a prized gift for lovers.
Given that I have my exam on Friday and Saturday I need all the luck I can get. Thanks Mom and Dad. You picked out the perfect gift. I love it.