Aquamarine

Overview

Aquamarine is the blue to greenish-blue variety of beryl, the same mineral as emerald, coloured by traces of iron. Its name comes from the Latin for "sea water". Unlike emerald, aquamarine usually forms large, clean crystals, so eye-clean stones are the norm and large sizes are affordable.

Colour

Aquamarine is valued for the depth of its blue. Pale stones are common; a medium, slightly saturated pure blue is the most sought after, and the deepest blues, sometimes sold under the trade name "Santa Maria" after a Brazilian locality, command the highest prices. Because aquamarine is light in tone, larger stones show their colour better than small ones.

Key properties

Where aquamarine comes from

Brazil's Minas Gerais has long been the main source. Nigeria, Madagascar, Mozambique, Zambia, Pakistan, Kenya and Namibia all produce fine stones.

Treatments

Most aquamarine is heat treated at moderate temperatures. Heating removes the yellow component that makes some stones greenish and leaves a cleaner blue. The result is permanent and cannot be detected, so it is generally assumed. Irradiation and coatings are rare.

Durability

With a hardness of 7.5–8 and no cleavage worth worrying about in daily wear, aquamarine is a practical choice for rings, including engagement rings, as long as the setting protects the corners and girdle from knocks.

Buying tips

• Look for colour you can see across a room. Deeper blue is rarer than size.
• Expect clarity. Visible inclusions should lower the price noticeably.
• Check the cut. A well-proportioned stone returns light evenly; shallow pavilions leave a washed-out "window" in the centre.
• Compare under daylight. Warm indoor lighting can make aquamarine look greener.

Care and cleaning

Use warm soapy water and a soft brush. Ultrasonic cleaners are usually safe for stones without fractures or fillings, but if in doubt, avoid them, and do not use steam. Store aquamarine apart from harder gems such as sapphire and diamond, which can scratch it.