The clear blue of aquamarine attracts jewellery makers and gem collectors alike. Its tone flatters all skin colours and harmonizes with all precious metals. It is relatively easy to cut and can often be found in innovative shapes, as cutters experiment with new forms.
Aquamarine is a member of the beryl group. Beryl commonly occurs as an accessory mineral in granites, and is usually found in cavities and in granite pegmatites. Beryl is usually clear, but iron content gives aquamarine its characteristic blue colour. Beryl crystals in some pegmatites grow to very large sizes, even up to 10 metres (30 feet) – aquamarine crystals of up to 1 metre (3 feet) long are not uncommon. Aquamarine is also sometimes found in stream gravels. It is generally free from inclusions, meaning that it is a durable stone; this is also why it is easy to cut. However, inclusions of biotite, RUTILE, PYRITE, and HAEMATITE are possible.
The major source of aquamarine is the state of Minas Gerais, southeast Brazil, especially the mines around Araçuí. The Brazilian mines produce stones of a characteristic colour with distinctive inclusions, and gemmologists can often determine the mine a particular stone came from based solely on a visual inspection.
Aquamarine is a fairly common stone, which makes it less expensive than the other gems of the beryl group, such as EMERALD. Its name derives from the Latin aqua for water and mare for sea, and many superstitions and legends about the sea have been attached to the gemstone over the years. It has been said to come from the treasure chests of mermaids. Sailors often took aquamarine with them to sea as a lucky charm to protect against shipwreck; sometimes the stone was carved with the image of Poseidon or Neptune, the gods of the sea. When it is immersed in water, the stone is practically invisible and the water in which it was immersed was long considered to have curative properties.
A top-quality aquamarine should be clear and free of inclusions. Today, the most popular stones are a clear blue, avoiding a tinge of either yellow, green or grey. In the 19th century, jewellery aficionados sought out sea-green gems. Because aquamarine's colour is usually pale, only larger specimens display any depth of pigment, but smaller stones are lively and decorative, especially when set with diamonds. Aquamarines are generally found in step cuts or as brilliants.
Today, most aquamarine is heat-treated to produce the favoured clear, blue colour. This treatment reduces ferric iron content and thus removes any yellow tinge. The treatment is permanent, stable and acceptable in the market. However, because aquamarine is sensitive to heat, it should be protected from excessive sun and heat exposure.
In addition to the mines of Minais Gerais, important sources of aquamarine include Kunar Province, Afghanistan; Mianyang City, Sichuan, west-central China; Embu, central Kenya; Zambezia, central Mozambique; Haramosh Mountains of Baltistan, northern Pakistan; and Buryatia Republic, eastern Siberia, Russia. Sites in the United States include Albany and Auburn, Maine.
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