One of the birthstones for June is the Moonstone.
Moonstone almost seems magical with a ghostly shimmering glow floating in a crystalline material. The Romans thought that moonstone was formed out of moonlight. Moonstone is a variety of feldspar, and the shimmer which is called “schiller” or “adularescence”, is caused by the inter-growth of two different types of feldspar, with different refractive indexes.
In Europe, Moonstone is considered the birthstone for June, although in the United States it shares that distinction with alexandrite and Pearl.
Moonstones come in a variety of colors. The body color can range from colorless to gray, brown, yellow, green, or pink. The clarity ranges from transparent to translucent. The best moonstone has a blue sheen, perfect clarity, and a colorless body color.
Sometimes moonstone will have an eye as well as a sheen. Another related feldspar variety is known as rainbow moonstone. In this variety of labradorite feldspar, the sheen is a variety of rainbow hues.
Fine moonstone is quite rare and becoming rarer. It is mined in Sri Lanka and Southern India. The rainbow variety can also be found in Madagascar.