What makes a moonstone glow?

One of my personal favorite stones is moonstone. Specifically blue moonstone. The stones are colorless but have a blue sheen that appears to float and move inside the stone. Often there are other secondary colors present like aqua green and yellow.

There is actually a gemological term for that floating sheen: it’s called Adularescence. The term originated with a city in Switzerland, Mt. Adualr (now St. Gotthard), that was one of the first sources of fine-quality moonstone. In fact, this type of moonstone was once called “adularia”.

Technically, adularescence is an optical phenomenon not a property of the stone itself. It only exists in the presence of light. The internal structure of blue moonstones called lamellae produce light scattering and interference. And it’s magical.

Of course what prompted this post was a necklace I just finished for a wonderful friend who loves moonstone as much I do. It features not only blue moonstone cabochons but a gorgeous strand of graduated blue moonstone beads.