What is rainbow moonstone?
According to the Gemological Institute of America (GIA), Rainbow moonstone is actually transparent labradorite. It’s not technically moonstone at all, but it’s very similar and has now been recognised by the trade as a gem in its own right. In fact, it’s so pretty, many prefer it to traditional moonstone. It is found in Madagascar, Sri Lanka, Mexico, Australia, India and Poland.
Above: polished traditional moonstone
Traditional moonstone is a beautiful, near-opaque gem favoured across the world for its adularescence – a billowy, moonlight-like sheen. It is considered an alternative birthstone for June. It was once known as adularia, and it takes this name from the Swiss city of Mt. Adular (now St. Gotthard), a major early source of top grade moonstone. René Lalique and Louis Comfort Tiffany famously employed it in their Art Nouveau designs. Craftsmen of the late nineteenth century Arts and Crafts movement also used the stone for their silver creations. During the 1960s, moonstone gained traction with the trend of flower power, and it again emerged in the early 90s for the New Age aesthetic (GIA).
It is made up of two feldspar minerals, orthoclase and albite. Initially these two minerals are intermingled. As the newly formed mineral cools, the two separate into stacked, alternating layers. As light falls between these layers, it is scattered in all directions, producing ‘adularescence’. This quality gives the surface of the gem a glowing appearance. The most prized gems are those that are more transparent and colorless, with more blue adularescence.
Rainbow moonstone is also made from a feldspar mineral, labradorite – this too contains albite. Although some websites will tell you it displays adularescence, that isn’t actually what’s happening, although you can be forgiven for thinking it. Like traditional moonstone, rainbow moonstone has thin layers of albite, and these produce a blue ‘schiller’ effect where the layer is thin, or a white effect where the layer is thick (IGS). A schiller effect is a variable optical phenomenon, related to sheen; in this case, it is a vivid iridescent play of color seen just below the surface (Mindat)
Above: rainbow moonstones on a black background to show labradorescence
Sometimes an iridescent optical interference of light gives the effect of blue with green and/or orange colors, a phenomenon known as labradorescence. This beautiful effect gives the gems their name “rainbow moonstones,” even though they’re not moonstone at all. So labradorescence (the effect seen in rainbow moonstones) and adularescence (the effect seen in traditional moonstones) are two different things. However, the name “rainbow moonstone” is now widely used and accepted in the gem trade.
What are the benefits of rainbow moonstone?
Every website I have visited confuses moonstone and rainbow moonstone. Please tell me if you find one that does not! Even those that acknowledge the two gems as having different compositions, then go on to discuss benefits of ‘rainbow moonstone’ that are typically attributed to moonstone, as if the two gems have the same qualities.
Traditional moonstone is associated with mental clarity and it also has plenty of lore associated with it. In Hindu mythology, it is made of solidified moonbeams – and the association with moonbeams is found in other too. The way the stone scatters the light is reminiscent of the full moon shining through a veil of thin, high clouds.
Rainbow moonstone, as we explained, is actually a type of labradorite and this gem is associated transformation and balance. It is thought to be effective at reducing anxiety. So two very different but highly positive beneficial associations.
Our moonstone/rainbow moonstone rings
We have a beautiful range of rainbow moonstone rings in our store. See below, L – R: