Aquamarine Quality Factors


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This 3.74-ct. princess-cut aquamarine’s prized medium-blue colour is highlighted by the 22 diamonds that surround it. The ring is an original, copyrighted design by Zoltan David. - Robert Weldon, courtesy of Nancy's Collection
In the commercial market, aquamarine competes with treated blue topaz for attention, but fine aquamarine sells for far more than equivalent-quality treated blue topaz.

Colour
Aquamarine’s colour range is very narrow: It can be blue, very slightly greenish blue, greenish blue, very strongly greenish blue or green-blue. The gem’s most valuable colour is a dark blue to slightly greenish blue with moderately strong intensity. In general, the purer and more intense the blue colour, the more valuable the stone. Most aquamarine is a light greenish blue.

32.10-carat Heart-shaped Brazilian Aquamarine
This superb 32.10-carat heart-shaped Brazilian aquamarine shows the gem's finest colour, a moderately strong, medium-dark, very slightly greenish blue. - Courtesy M.Chung Gemstones and Fine Jewelry Co.
Although some buyers prefer the more greenish natural colour, most of the aquamarine in the market has been heat-treated to give it more of a pure blue.

Fashioned aquamarines often have to be fairly large—generally over 5 carats—to show intense, dark colour. Although small gems are rarely saturated enough to be attractive, stones from some mines in Africa—Nigeria, Madagascar and Mozambique, for example—are known for intense colour in sizes under 5 carats. For this reason, smaller, top-colour stones might sell for more per carat than larger stones of the same colour.

Clarity
Most faceted aquamarines are eye-clean. Some crystals might contain liquid inclusions, but clarity characteristics are few or absent in most finished gems. Stones with eye-visible inclusions are usually fashioned into cabochons, beads or carvings.

Aquamarine carving
Carvings are popular for translucent to opaque aquamarine. - Courtesy Neoart Peru
Faceted Aquamarine
Faceted aquamarine usually has no eye-visible inclusions. - Courtesy Dudley Blauwet
In some beryl crystals, there are enough parallel inclusions—usually long hollow or liquid-filled tubes—to allow cutters to fashion the rough to show a cat’s-eye.

Greenish Aquamarine Cabochon
This very greenish aquamarine cabochon has enough parallel inclusions to display a cat’s-eye.
Cut
Aquamarines can be cut into almost any shape, but cutters often fashion them as emerald cuts or as round or oval brilliants. The rough is fairly plentiful, so well-cut stones are fairly common. The gemstone’s hardness and transparency make it popular with designers, artists and carvers. Gem sculptors use aquamarine for fantasy cuts and ornamental objects.

Aquamarine
Aquamarine can be cut in a variety of standard shapes.
Emerald-cut Aquamarine
Emerald cuts are among the common aquamarine cutting styles. - Courtesy ICA
The gem is pleochroic, which means it shows different colours in different crystal directions—in the case of aquamarine, they’re near-colourless and strong blue. Fortunately, the blue pleochroic colour corresponds with the cutting orientation that retains the most weight, with the table facet aligned parallel to the length of the crystal.

10.37-carat aquamarine
Aquamarine is a great medium for artistic designer cuts like this 10.37-carat beauty. - Lydia Dyer, gem courtesy John Dyer & Co.
Aquamarine Designer Jewelry
Aquamarine that’s too included for faceting is often carved and set into designer jewellery. - © GIA and Tino Hammid
Carat Weight 
Aquamarine crystals come in sizes from very small to very large — some even up to 100 lbs. (45 kg). While large stones are readily available, it’s difficult to use them in jewellery, so there’s less demand for them, except as centre stones. As a result, per-carat prices tend to decrease for sizes above 25 carats.

Many very large aquamarine crystals have been discovered. The largest Brazilian aquamarine on record was found in 1910, in Minas Gerais, Brazil. It weighed 244 lbs. (110 kg) and measured 19 in. (48 cm) long and 15 in. (38 cm) in diameter.