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Definition: moonstone from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Translucent, pearly variety of potassium sodium feldspar, found in Sri Lanka and Myanmar, and distinguished by a blue, silvery, or red opalescent tint. It is valued as a gem.

Summary Article: Moonstone
From Guide to Gems

Long considered a sacred stone in India, moonstone is often believed to be moonlight in a magical, solid form. A virtually colourless stone, it is distinguished by a bluish shimmer that moves across its face as the stone is moved.

Moonstone is a variety of ORTHOCLASE, a member of the feldspar group of gems.

Sri Lanka is the most important source of moonstone, both in terms of volume and quality. There it is mined by hand, a slow and laborious process. It is one of the few gemstones found in situ in Sri Lanka (Meetiyagoda, southern Sri Lanka) – the others are exclusively found in gravel.

Moonstone's magical shimmer, often known as schiller, is caused by the intergrowth of orthoclase and ALBITE, another feldspar variety. To show it at its best, the gem is generally cut as a cabochon, and the higher the dome, the more radiant the shimmer. It is also sometimes carved into ornaments. Moon faces are a popular theme, but over the years it has even been used in cameos. Moonstone's shimmer is distinctively blue. If the sheen displays in a variety of hues, the stone is known as ‘rainbow moonstone’, which is actually a variety of LABRADORITE, another type of feldspar.

Very popular in the Art Nouveau jewellery of the early 20th century, today moonstone is once more much in demand. It is rare – and becoming rarer – which makes it reasonably expensive. Because it is expensive, moonstone is sometimes imitated, using either glass or decolorized AMETHYST. In addition to its beauty, moonstone is believed to possess strong protective and healing powers.

Cabochon-cut moonstone gem

© 2003 Philip's

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