Aquamarine

Aquamarine is just one member of the beryl family. Its siblings include such notables as emerald, heliodor (golden beryl), and morganite (pink beryl). Aquamarine is mined on almost every continent, but the most prolific mines historically have been found in Brazil and, most recently, in African nations such as Nigeria and Mozambique. Because of its geologic growth process, aquamarine crystals can grow to great size-even pieces weighing more than 100 pounds are not unheard of.

History and romance. Aquamarine-Latin for “water of the sea”-is the birthstone for Pisces and Aries folks born in March. According to legend, this seawater gem will protect sailors on their journeys. Aquamarine is not only appropriately named but also fits the flip-flop, vacillating nature of Piceans: It can be greenish-blue, bluish-green, or anything in between.

Brazilian aqua’s history begins in the state of Minas Gerais. While the aqua of the early 1900s was a deep, dark, saturated blue, today you’re most likely to encounter a much lighter and slightly less saturated Brazilian aquamarine. At present, the more saturated colors are coming from Nigeria, Madagascar, Malawi, Mozambique, Zambia, Zimbabwe, and Afghanistan. There are also lighter aquas from India, especially from the north and from Orissa. Madras also produces a small amount of aqua in prized colors. China produces a lot of aquamarine, but most is so light in color-just a hint of blue-that some dealers actually promote it as “white aqua.” You can even find aquamarine right here in the United States, especially around North Carolina’s Hiddenite area.

Color variations. One could conjure up all sorts of variations of blues and greens that would fit a gem whose name means “seawater,” depending on which body of water one had in mind. Color is a matter of personal taste when looking for a fine aquamarine, but most customers expect a little green mixed in with a mostly blue hue. Some aquas contain a lot of green, possibly even slightly more green than blue, but these are considered much less desirable than predominantly blue aquas. Aquas from Africa, some of which have no green component, are among the most desirable of all.

The subtle color description of “bluish-green” for an aqua can also describe emerald and even green beryl. While there are no scientific dividing lines among the three, a definition of sorts-much to the dismay of those who enjoy green beryls-describes emerald as having enough green to be “pleasing.” In more scientific nomenclature, emerald green is more saturated and darker in tone than green beryl. The difference between these two and aqua is also in the tone and saturation of the hue, with an emphasis on the blue component. The green of the aqua should be like that of green beryl, less saturated and lighter in tone than would fit the definition of emerald. Plus, the aqua should have a strong blue component that green beryl won’t have. (Note the color of the two aqua crystals in the photo on the preceding page.)

Qualities. Most aquamarine is typically “eye-clean”-that is, few inclusions are visible without magnification. Some aquas show long, thin, tube-like inclusions running the length of the crystal. If enough of these tubes are present, a cabochon cut can create a wonderful aquamarine cat’s-eye.

Value. Because aquas are expected to be eye-clean, color is most important in establishing value. The more saturated and darker-toned pure-blue aquas command the highest prices. To the purist, aquas with some green component-which helps prove natural color origin-are highly prized. Greenish aqua is rare because so much is lost to thermal enhancement. The Nigerian material that was uncovered in the early 1990s reportedly did not react to thermal enhancement and whetted people’s appetite for the greener shades.

Enhancement. Most naturally greenish-blue aquamarine will be heated to remove the green component. In fact, one possible way to determine whether or not an aqua has been thermally enhanced is to look at the gem’s pleochroic colors with a dicroscope or Polaroid plate. Because aquamarine is a dichroic gemstone, it should naturally reveal two colors, green and blue. But heated aquas will tend to show two tones of the same blue color.

According to laboratory gemologists, however, this is not necessarily true of all naturally colored aquamarines, so one needs to look at inclusions to see if they’ve been damaged by heat treatment. But since most aquamarines are free of inclusions, color origin can’t always be identified. Finding a reputable supplier who buys directly from the source is one way to determine the color origin of an aquamarine.

Pricing. Since most aquamarine is assumed to be thermally enhanced, current pricing seems unaffected by origin. But it might be wise to note the trend in other gem markets, such as those for sapphire and ruby, where prices of naturally colored stones are starting to outpace prices of enhanced stones. Estimated prices on a standard fine-quality 5-ct. aquamarine of medium-blue to medium-dark-blue color range from about $200 to $250 per carat. Larger gemstones generally command a higher price per carat, but because aquas can be found in very large sizes, the price per carat actually drops for stones that weigh more than 50 cts. Stones of less than 20 cts. are in demand, especially 5-ct. to 10-ct. sizes. Aqua is less likely to hold its color as carat weight decreases.

Care and cleaning. One member of the beryl family, the emerald, is a more fragile gem than most. Aquamarine, however, is durable and wears well. But to prevent dust from scratching it-or any other gem with a hardness of 7 or less (beryl has a hardness of 7 to 7.5)-rinse aquas clean of dust before wiping with a dry cloth.

Bench settings and precautions. As with most colored gems, it’s preferable to pull the stone from the ring before performing any repair work. To avoid the possibility of thermal shock to liquid inclusions, don’t apply heat directly to the gem. Heat can actually turn some African aquas gray.

Recommended Reading. For more information, see the following references:

Dr. John Sinkankas, Emerald and Other Beryls, Geoscience Press, 1981.

Gary Bowersox, “Aquamarine from Afghanistan,” Gems & Gemology, Winter 1985, pp. 192.

Special thanks to Bear and Cara Williams of Bear Essentials, Stuart Robertson of Gemworld International, and Tom Cushman of Allerton Cushman & Co.