Moonstone Buying Guide


moonstone buying - victorian amethyst and moonstone pendant
Victorian pendant featuring an amethyst surrounded by transparent moonstones, set in 18k gold. © The Parisian Flea of Hampden. Used with permission.

With a mysterious sheen reminiscent of moonlight, moonstone has been treasured for thousands of years. This effect, called adularescence, is caused by fine layering of feldspar minerals, which catch the light and shimmer below the gem’s surface. Due to its use as a birthstone for those born on Mondays or as an alternative to pearl and alexandrite for June births, this gem has recently gained popularity. Still, prices are low for all but the top-quality moonstones, and moonstone buying is fairly straightforward. Nevertheless, be wary of simulants and keep in mind the material’s softness when choosing a jewelry setting.

Moonstone Buying and the Four Cs

The IGS moonstone value listing has price guidelines for rainbow moonstone (peristerite), labradorite, white cat’s eye, white adularescent, and other color moonstones.

Color

Moonstone color can be separated into body color and adularescence (sheen) color. Ideally, moonstones exhibit a transparent, colorless body with pure blue, medium-toned sheen.

Antique moonstone ring in 18k gold. This moonstone exhibits a beautiful blue sheen. © The Parisian Flea of Hampden. Used with permission.

However, this feldspar can occur in many colors. Any body color detracts from the value, and unattractive green hues will significantly lower the gem’s price. Peach pink hues are popular, but not as highly regarded as colorless stones. Brown, yellow, and blue hues also occur.

moonstone buying - pendant_orange_moonstone
A simple pendant with a peach moonstone with bright white shimmer. “Peach Moonstone Orb Pendant” © Gina Pankowski. Used with permission.

Adularescence can also occur in many colors. “Rainbow moonstones” from India exhibit a multi-hued sheen, often blue and yellow. White is another popular sheen, though not as valuable as blue.

moonstone buying - rainbow moonstone pendant
Argentium silver, hand fabricated pendent with 2.48 ct Indian rainbow moonstone. By Stacia Woods. © Jewels by Stacia. Used with permission.

Clarity

Moonstones should be eye clean. However, inclusions are usually visible with magnification. “Caterpillar” or “centipede” flaws can confirm the stone’s identity as a moonstone.

Some stones may exhibit chatoyancy, or a cat’s eye effect. Especially rare specimens show asterism when properly cut.

moonstone buying - star moonstone
A bright peach star in a white moonstone, set in 22k gold in a sterling silver ring. “Pentafoil Ring in Sterling Silver and 22K Gold, Moonstone with a Star” © Gina Pankowski. Used with permission.

Cut

To best display adularescence, moonstones are cut in a high cabochon.  Those with a flatter cut won’t exhibit as much sheen. Gem cutters fashion other gems into beads or facet them for greater brilliance.

moonstone buying - moonstone and blue opal ring
The high cabochon in this moonstone brings out its shimmer. “Moon Over Ocean Ring in 18k gold Moonstone and Blue Opal” © Gina Pankowski. Used with permission.

Carved moonstones are popular, but some carvings hide inclusions or fractures in the stone, or reduce the adularescence. However, well-carved specimens are simply mesmerizing.

Freeform carving of a 24.29 ct Tanzanian moonstone by Larry Woods. © Larry Woods.  Used with permission.

Carat

Moonstones below one carat are readily available. Fine specimens over five carats are rare, and the price per carat doubles. Prices double again at the ten-carat mark due to increased rarity.

Jewelry Considerations

Although a popular gem, moonstones are relatively soft, sitting at only 6-6.5 on the Moh’s scale. They are also susceptible to chipping. Therefore, protective jewelry settings or use in pendants or earrings are recommended to keep the stone from damage.

Treatments and Simulants

Though uncommon, a treatment that impregnates moonstones with an organic substance has been found by the Gemological Institute of America (GIA). This procedure improves adularescence. Under ultraviolet light, these specimens fluoresce.

You’ll more commonly find other materials used as moonstone simulants. Some unscrupulous sellers will offer leaded glass, opal, or labradorite as moonstone. The presence of caterpillar inclusions indicates a true moonstone, while swirls and bubbles present under magnification signal glass.

moonstone buying - opalite earrings
A type of glass, opalite makes a particularly convincing moonstone simulant. (Don’t confuse it with opaline, an opal-like silica found in bamboo trees). “Christmas 2013 earrings silver and black,” opalite, Swavorski crystal, and sterling silver, by j3jewelry. Licensed under CC By-ND 2.0.

About the author
Addison Rice
A geologist, environmental engineer and Caltech graduate, Addison's interest in the mesmerizing and beautiful results of earth's geological processes began in her elementary school's environmental club. When she isn't writing about gems and minerals, Addison spends winters studying ancient climates in Iceland and summers hiking the Colorado Rockies.
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