Aquamarine (Lat. aqua marina, water of the sea) is the March birthstone and a silicate mineral with the chemical formula Be3Al2(SiO3)6. All minerals of the beryl group consist of beryllium aluminium cyclosilicate and aquamarine is its turquoise or blue variety.
If this mineral has a very deep blue colour, you might find it called maxixe. The beryl minerals belong to the cyclosilicates, a sub-group of silicates, and as the name implies there’s a ring structure in the crystal.
The presence of iron ions alters the colour. Fe2+ ions cause a crystal to look pale blue, whereas Fe3+ make it yellow-golden. A combination of both ions produces a dark blue colour, maxixe. Sunlight or heat treatment lighten the mineral. Aquamarine is transparent and 7.5-8 on the Mohs scale of mineral hardness, with 7-10 being able to scratch the surface of glass, and 1-6 being damaged by a scratching knife along their surface. Diamond is the hardest at 10 and talc the softest at 1.
Aquamarines have been used in royal jewellery for hundreds of years and in the English crown there’s a 920-carat gem. Already at the end of 1300, the first pair of lenses was made from aquamarine for spectacles. The etymology of beryl is quite interesting and the German word for eyeglasses, Brille, might not be so illogical after all.
The crystals found in many locations around the world can become large and the heaviest one of gemstone quality found to date weighs 110.5 kg. The largest cut gem can be seen in the National Museum of Natural History, part of Smithsonian Institute.
Jewellery containing aquamarines can be cleaned quickly under running water. The gemstone is brittle so please treat it with care.