Aquamarine Buying Guide
If you want a stone with the pure sparkle of clear blue seas, look no further than aquamarine. Whether on its own or paired with other gems, aquamarine is simply enchanting. Commonly associated with sailors and the sea, some believe this gem has protective powers and can even bring good health. The modern birthstone for March, aquamarine has become a popular gem for engagement rings, too. Watery blue to blue-green aquamarines make great additions to jewelry as well as gemstone collections. Although these gems have a moderate price range, the best displays of their beautiful color require large stones. For buyers on a budget, synthetic pieces and alternative blue or blue-green stones may offer the best performance and value.
Aquamarine Buying and the Four Cs
The IGS aquamarine value listing has price guidelines for faceted and cabbed aquamarine.
Aquamarine, the beryl variety with blue to blue-green hues, gets its color from iron speciation in the crystal. Unlike other colored gemstones, aquamarine’s value comes primarily from its tone rather than hue and saturation. Darker tones fetch higher values, and dark stones with some grey will cost more than lighter stones.
Still, light-tone stones can be quite beautiful. Some connoisseurs even prefer gems a few shades lighter than the darkest aquamarines available. However, stones called “white aquamarine” are not aquamarine. They should be labeled as goshenite or colorless beryl.
Naturally greenish blue in hue, aquamarine stones tend to have 5-30% green hue. Heat treatment removes some of the yellow, leaving the stone bluer. This process doesn’t lower the value of aquamarine. It can actually raise the price because of the color improvement. Although gems with less green hues are generally preferred and more highly valued, some consumers do prefer the sea-green colors of natural aquamarine. Such gems may sell better in independent jewelry shops for their unique hues.
For faceting, crystals should have eye-clean clarity grades (VS or VVS). Visible inclusions will lower an aquamarine’s value. Some highly transparent aquamarines have an icy quality. This brilliance will greatly add to the gem’s value, even if the aquamarine has a very light in tone.
This natural aquamarine specimen, perched on a matrix of albite, could hardly be called “rough.” It shows great hue, tone, and clarity.
Regal, blue Aquamarine from Shigar Valley, Pakistan from The Arkenstone – iRocks.com on Vimeo. © Rob Lavinsky, www.iRocks.com. Used with permission.
Highlighting the unique character of included stones has recently become a popular jewelry trend. For aquamarines, such designs can have spectacular effects, making the stones appear like glacial ice.
Gem cutters tend to cut aquamarines to enhance their tone. You’ll frequently see aquamarines with deep emerald cuts and Barions. However, you can also find almost any cut. Lapidaries have created designer cuts and sculptures using large aquamarine crystals.
Since aquamarines below 5 carats may not exhibit desirable tones, you’ll more commonly see these gems as featured stones rather than accents. However, like most other beryls, aquamarines do occur in large sizes. Thus, the price per carat doesn’t grown exponentially. In fact, the price per carat drops at around 25 carats because the stones become too large for jewelry. Some very large aquamarines are used for carving.
The largest faceted aquamarine, the Dom Pedro, resides at the Smithsonian Institute National Museum of Natural History in Washington, DC.
Rare star and cat’s eye aquamarines display asterism and chatoyancy, respectively. In beryls, hollow tube inclusions cause these optical effects. When properly cut, these effects are delightful. A cat’s eye cabochon will cost about the same amount as a faceted gem with the same color. Star aquamarines will command even greater values.
Aquamarine Heat Treatment
Many aquamarines receive heat treatments to reduce their yellow hues and make them bluer, often at the mines while the material is still rough. This treatment, undetectable with modern gemological equipment, occurs at a low temperature. The treatment’s outcome varies based on the stone’s origin and chemistry. However, the treatment doesn’t affect the tone, only the hue of the stone. This permanent enhancement doesn’t require extra care.
Some material can’t receive this treatment due to flaws in the crystal structure or won’t heat blue because of its origin. Therefore, buyers should beware of greenish rough that a seller claims will heat to a fine blue.
Maxixe aquamarines, named after the Maxixe mine where they naturally occur, are blue beryls that get their color from irradiation, not iron. This unstable color will fade over time. Maxixe aquamarines are sometimes created in labs by irradiating beryls to a deep blue hue. These gems exhibit strong colorless and blue dichroism. A spectroscope examination can easily identify them.
Aquamarine Buying: Alternatives
You can readily purchase synthetic spinel gems with deep aquamarine colors. They might even come closer to your desired jewelry color than aquamarines at a better price point.
Heat treatment of zircon can also result in a desirable blue color. However, zircons are subject to chipping and can’t be cut in a number of styles. Nevertheless, they exhibit good brilliance and color in a lower price range than aquamarines of similar properties.
Irradiating and heating colorless topaz can also produce a lovely blue color, much like fine aquamarine. Though somewhat subject to chipping, blue topaz makes a great substitute for aquamarine for those on a budget.
Any stone with the right blue hue may be passed off as aquamarine. Buyers should beware of stones priced too cheaply for their quality. If you’re unsure whether your stone is a topaz or an aquamarine, a simple test with a diamond tester or a loupe exam can make the determination.