Moonstone - it is said if you give your lover a moonstone necklace when the moon is full you will always have passion with each other. Moonstone is a very personal stone. It is a reflection of the person who owns it. It does not add or detract, only shows how it is. This is why the moonstone is said to perceive that which "is".
it looks like captured starlight...like something the elves of the Tolkien universe would make like they did with the gift of their beloved star that Galadriel gave Frodo when the Fellowship was leaving Lothlorien