Rainbow Moonstone Cabochon

This is an exquisite rainbow moonstone has an extraordinarily beautiful blue shimmer. Ancient Romans theorized that its earthly shimmer, was formed from frozen moonlight but (sorry to disappoint) it is the mineral feldspar, quite terrestrial in origin. The shimmer, which is called adularescence, is caused by the intergrowth of two different types of feldspar, with different refractive indexes. I still think that is pretty special, just like this specimen!