Picture blue moonlight shining brightly through fog and you’ll understand why this variety of feldspar is named moonstone. Its shimmering sheen moves through the stone like moonlight.

The ancient Romans and Hindus thought that moonstone, with its ghostly glow, was literally formed from moonlight. Legends say that you can see the future if you hold a moonstone in your mouth during a full moon.

Moonstone is a variety of the feldspar and the shimmer, which is called schiller or adularescence. It is caused by the intergrowth of two different types of feldspar, with different refractive indexes.

In Europe, moonstone is considered the June Birthstone. In the United States, it shares that distinction with alexandrite and pearl.

Fine moonstone is becoming rare, although lower quality moonstone is widely available and can be quite affordable.

This gem come in a variety of colors. The body color can range from colorless to gray, brown, yellow, green, or pink, though blues are rare. The clarity ranges from transparent to translucent. The best has a blue sheen, perfect clarity and a colorless body color.

A closely related feldspar variety is known as rainbow moonstone. In this variety of labradorite feldspar, the sheen is a wide range of rainbow hues.

Moonstones are usually cut in a smooth-domed oval cabochon shape to maximize the effect. Sometimes they are carved to show a man-in-the-moon face.

Moonstone has a hardness of 6 to 6.5 on the Mohs scale. It should be stored away from other gemstones to prevent scratching andcleaned with mild dish soap. Use a toothbrush to scrub behind the stone where dust can collect.

The post Moonstone – A Shimmering Gemstone appeared first on GIA 4Cs Blog.