Moonstone

Formerly, it was believed that the moonstone was fossilized rays of the moonlight. Evidence of this was supposed to be a mysterious blue glow appearing on its surface as it rotates. In fact, the moonstone is one of the feldspars, the most abundant mineral in the earth's crust. 

According to legends, whoever comes into possession of a moonstone will be endowed with the ability to foretell the future.

Please note that the price is per crystal, and not for multiple.