Moonstone: Properties, Facts and Photos

Contents 1. What is Moonstone? 2. Moonstone Vs Rainbow Moonstone 3. More About Moonstone 4. Article Photos 5. Shop Moonstone

What is Moonstone?

Moonstone is a variety of orthoclase feldspar that exhibits a unique optical effect known as adularescence. This produces a soft, milky glow that appears to float just below the stone’s surface when viewed from certain angles.

Adularescence is caused by the scattering of light between thin layers of feldspar within the crystal. This effect is a type of schiller, a general term used in mineralogy to describe optical effects caused by internal structures within a crystal.

The word adularescence comes from the mineral adularia, a rock-forming variety of orthoclase named after the Adula Alps in Switzerland, where it was discovered.

Moonstone is composed of different feldspar minerals, with the amounts varying from one stone to another. The most common is adularia, followed by albite. Although these minerals have similar chemical compositions, their crystal structures differ.

Moonstone can be translucent to transparent and occurs in several colours, including pink, cream, white, and black. These variations depend on the relative amounts of feldspar present.

Gemstones that exhibit optical effects are usually shaped as cabochons because this cut enhances the effect, which in the case of moonstone is adularescence.

Moonstone has been described as having the appearance of lunar light floating on water, which is believed to be how the name 'moonstone' came about.

Although a subtle white sheen is most commonly observed, hues of orange or blue can also sometimes be seen.

Moonstone Vs Rainbow Moonstone

The name 'moonstone' causes so much confusion because it's often mistaken for rainbow moonstone. Rainbow moonstone is a type of white labradorite, so the two materials are geologically different.

This whitish-grey feldspar (white labradorite aka rainbow moonstone) exhibits vivid flashes of blue caused by an optical effect known as labradorescence.

Because rainbow moonstone has become so popular, it has flooded the internet to the point where geological accuracy has been overridden.

It’s now extremely difficult to find photographs of genuine moonstone. Even when using the correct geological terms, such as orthoclase, adularia, or 'real moonstone', most images that appear are rainbow moonstone.

Genuine moonstone is notoriously difficult to photograph because its soft, billowing sheen can easily be lost with the wrong lighting. Therefore, in some photographs, the stone can look plain and uninteresting, especially when compared to the blue flash often captured in rainbow moonstone.

More About Moonstone

Moonstone has a long history and has been used as a gemstone for thousands of years. Scholars believe that a white moonstone was the third stone in the second row in the biblical garment known as the high priest breastplate.

The Romans used moonstone in jewellery and believed it was moonlight in a magical solid form. It was especially revered during a full moon.

In Europe during the Middle Ages, it was believed that if you gazed at moonstone for long enough, you would fall into a deep sleep that would predict the future.

In India, moonstone has long been considered sacred and is still widely used today.

Moonstone has long been used in jewellery, but it became even more popular in the early 20th century. It was widely used in Art Nouveau jewellery because designers were drawn to stones with a mystical appearance and unique properties. It was also very popular in the 1960s. 
 
Some of the world's finest moonstone comes from Myanmar (formerly Burma) and Sri Lanka. Deposits can also be found in Brazil, India, Madagascar, Mexico, Tanzania and the USA.

On the Modern and Mystical Birthstone Charts, moonstone is the birthstone for June. Pearl, alexandrite and emerald can be used as alternatives. On the Ayurvedic Chart, moonstone is the birthstone for September.

On the Mohs scale of mineral hardness, moonstone grades 6 to 6.5. It should always be handled carefully because it tends to break along planes of weakness within its crystal structure.

Article Photos

The moonstone at the top of our article is a pink moonstone, although its colour is not distinctively pink. It exhibits adularescence, although we were not able to capture it in our photo.

The second photo, which is white labradorite, is usually sold as rainbow moonstone. Photo: Courtesy of Géry Parent.

Pop-up photos
Adularia: Courtesy of Ron Wolf. Albite (with epidote): Courtesy of Stan Celestian.