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Aquamarine: A Designer’s Delight

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An 18-karat yellow gold ring with an aquamarine centre stone surrounded by round brown diamonds and dotted with pink tourmaline.  By BRUMANI

An 18-karat yellow gold ring with an aquamarine centre stone surrounded by round brown diamonds and dotted with pink tourmaline. By BRUMANI

You can lose yourself in the watery, greenish blue beauty of aquamarine. In fact, the gemstone’s name is derived from two Latin words: ‘aqua’, meaning ‘water’ and ‘marina’, meaning ‘of the sea’. A green-blue to blue variety of the mineral beryl (the same mineral as emerald), aquamarine is usually a light pastel greenish blue.

By the Gemological Institute of America (GIA)

Lore has it that the beryl protects those who wear it against foes in battle or litigation and makes the wearer unconquerable and amiable. It is also said to quicken the intellect.

Aquamarine competes with treated blue topaz for attention, but fine aquamarine sells for far more than equivalent-quality treated blue topaz.

Cutters often fashion aquamarine, the birthstone for March, as emerald, round or oval brilliant cuts. Rough is fairly plentiful, so well-cut stones are usually available. 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 crystals  are known to be large in size and relatively clean and well-formed, making them particularly valuable to mineral specimen collectors.

Journey of the Stone

Brazil has been the world’s  most  important source of gem-quality aquamarine since  1811, when  a miner found a large 7 kg aquamarine crystal in a riverbed. It was the first large aquamarine crystal ever recorded.

Since then, many large aquamarine crystals  have been discovered. The  largest  on record, found in 1910 in Minas Gerais, Brazil, weighed 110 kg and  measured 48 cm long and  38 cm wide. Although the fine blue- green crystal was water-worn, most  of it was gem quality  and  so transparent people were able to read printed pages  through the length of the crystal. Since the discovery of this record-holding crystal, millions of carats  of fine aquamarine have been found in the thousands of mines throughout the region.

Pakistan is another significant producer of aquamarine. Pegmatites produce light greenish blue to blue  crystals, some  up to 30 cm long by 12 cm wide. Miners  also find inky blue  crystals. Less significant sources are Australia, Kenya, Madagascar, Mozambique, Nigeria, the US and  Zambia.

China recently became the world’s leading producer of small, commercial-quality aquamarine. Most of the stones measure about 6-4 mm, and commercial-grade sizes rarely exceed 10-8 mm, or about 2 carats.

Most Chinese aquamarine is clean and very pale. It’s widely used in most of the mass-market jewellery available through home-shopping networks and other high-volume outlets.

Connoisseur’s Guide

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.

Fashioned aquamarines often have to be fairly large – generally more  than 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.

Although some buyers prefer the more greenish natural colour, most  of the aquamarine in the market is heat-treated to give it more of a pure blue. Some dealers leave greenish blue aquamarine untreated and use its uniqueness to promote it because the untreated colour sets it apart from its competitor, treated blue topaz. Because  of widespread concern about treatments, untreated gems – like natural-colour aquamarine – appeal more  than ever to informed consumers.

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.

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 common to find. The gem is pleochroic, 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 which aligned parallel to the length of the crystal.

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.

Treatments

Nearly all the blue aquamarine found in jewellery results from heat treatment of bluish green, greenish yellow, or even brownish yellow gems. Heat  treatment is undetectable, and  the treated colour appears to be permanent. The most common aquamarine imitations are treated blue topaz, pale blue glass, and synthetic blue spinel coloured by cobalt. Standard gemmological tests easily distinguish aquamarine from its imitators.

Care and Cleaning Guide

Aquamarine is 7.5 to 8 on the Mohs scale of mineral hardness, so it is a durable gemstone for jewellery as long as it is treated with care to protect it against scratching and hard knocks. Heat exposure is not recommended for aquamarine, but the colour is stable against light exposure. Aquamarine can be attacked by hydrofluoric acid.

Warm soapy water is always a safe cleaning method for aquamarine. Cleaning by ultrasonic and steam cleaners is usually safe unless the stone has liquid inclusions or fractures. Rarely, aquamarine might be fracture-filled. Such stones should only be cleaned with warm soapy water.

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