Emeralds originate from a mineral called beryl, and are green as a result of traces of the element chromium. Some beryl with vanadium is also green, and in the US can be called emerald. This is not the case in Europe and the UK, where this mineral is not permitted to have the name emerald.
Geologists have a hardness scale for minerals, and it is called the Mohs scale of hardness. On this scale, emeralds are 7.5-8, the scale going up to a maximum of 10.
Most emeralds have inclusions, or imperfections within the gemstone itself, which means that they are weaker than those without inclusions and are not very resistant to breakage.
Emeralds without some form of inclusion are particularly rare, and because of this are very valuable. Tiny liquid-filled inclusions within the gemstone are known as ‘jardins’, and have the appearance of a garden.
The value of an emerald is determined, as with other gemstones, by the 4 ‘C’s. They are Color, Cut, Clarity and Crystal.
The majority of emeralds are treated with oils to improve their clarity. Cedar oil or synthetic oils may be used for this purpose. In the USA, emeralds which have been treated in this way must be disclosed as such at the time of sale.
Many countries have emerald mines, however the best-known is probably Colombia. It is in this country that a particularly rare type of emerald, the trapiche, is found. The trapiche emerald has carbon impurities which give it a six-pointed radial pattern inside the gemstone.
Pakistan, Austria and Egypt are also noted for their emerald mines, however many other places around the world have these mines.
Synthetic emeralds have been made by various processes, many of them consist of growing a layer of synthetic emerald over a small crystal of beryl.
Emerald is the traditional birthstone for the month of May, and also the traditional stone for the astrology signs of Taurus and Cancer. In some places, emeralds are traditionally given for the 55th wedding anniversary, and sometimes for the 20th and 35th wedding anniversary.
Major emeralds which have been discovered include the Gachala emerald from Colombia, which weighed 172g, and the 37.82 carat Chalk Emerald also from Colombia.
It is possible to cut an emerald into any one of a number of shapes, but the most popular is the ‘emerald cut’, as it shows off the gemstone so well. Other cuts can be oval, marquise, pear or round.
Read more facts about emeralds and emerald rings at Sarah Carter’s site Emerald Rings Guide. You can also get facts on antique emerald rings. This article, Emeralds – A Short Guide is available for free reprint.