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.
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.
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.
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.
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.
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.