This gemstone has the ability to interact with light in such a way that it resembles moonlight shining across the ocean or through a veil of clouds. Historically, legends tell of moonstone bringing its wearer good luck.
The captivating gem is generally semi- transparent to translucent, displaying a milky, silvery white sheen through to the more desirable blue sheen.
This blue, in a more transparent stone, is the most valuable, sought-after, and difficult to source form of moonstone. Other colours include beige, brown, yellow, reddish- brown, greenish, orange, and grey.
Moonstone is generally readily available, including the cat’s eye (chatoyant) variety, but is scarcer in higher quality material and larger sizes.
An interesting and characteristic feature that may be found in these specimens is an inclusion called centipedes – long, minute tension cracks with shorter perpendicular cracks overlapping.
Moonstone is a member of the feldspar mineral group, specifically being composed of two feldspars – orthoclase and albite.
These two varieties grow parallel to each other within the stone, causing light to
scatter and reflect off the multiple layers producing the silvery white phenomenon known as ‘adularescence’ or ‘schiller’.
When these layers of orthoclase and albite are thinner and consistently spaced, the adularescence effect is progressively bluer.
This adularescence gives moonstone its prized ‘glowing’ appearance, which rolls over the stone as you move it and change the angle of view. This makes it ideal for a cabochon cut – particularly with dimensions uniform and not too flat – as this enhances and highlights this sheen.
The word adularescence comes from the gemstone’s original name, ‘adularia’, after Mount Adular in Switzerland where the first high-quality material was found.
Today, gem-quality moonstone is found in locations including Madagascar and Tanzania, with the finest in Sri Lanka, southern India, and Myanmar (Burma) in limited supply.
When cut correctly en cabochon, this multi- talented stone may also exhibit chatoyancy, including asterism, with a four-rayed star caused by the same layered feldspar structure that causes the adularescence.
Other cutting techniques include faceting, which offers increased brilliance, and carving, such as a face representing the ‘man-in-the-moon’.
With a hardness of 6–6.5 on Mohs’ scale, and cleavage – a plane of weakness – in two directions, this gem is better suited to pendants, earrings, and brooches rather than rings.
To care for moonstone, it’s best to steer clear of ultrasonics and steam cleaners and opt for warm soapy water instead. It is susceptible to damage when exposed to a sudden shift in temperature, high heat, or hydrofluoric acid.
This gemstone was a popular choice among jewellery artisans of the Art Nouveau era, including Louis Comfort Tiffany and Rene´ Lalique. The stone can be found featured
in notable works such as special, singular commission carvings by Faberge´ and oriental-inspired Art Deco clocks by Cartier.
Like many gemstones, imitants are available on the market, either intentionally designed to fool or coincidentally resembling moonstone. Some of these include synthetic white spinel heat-treated to give the adularescence effect, opalescent glass, chalcedony with a milky consistency, and even heat-treated amethyst.
To this day, this beautiful gemstone offers jewellery design with the same romanticism and mysticism we associate with moonlight.
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