Emerald is a quality of beryl coloured green by the presence of chromium. Its characteristics are the green colour (with shades from blue – green to yellow – green), the vitreous lustre and a hardness of 7 on the Mohs scale of mineral hardness.The evaluation of emeralds is based on integrity of the gem, cut, colour and transparency; in particular, these last two parameters are the most important. Unlike diamonds, the emerald integrity is evaluated to the naked eye. Usually, emeralds have many surface breaking fissures and inclusion, therefore, an emerald that does not present those sorts of imperfections is considered defect less.Emeralds are naturally found by searching through granites, metamorphic and hydrothermal, as well as through secondary alluvial deposits. The most important mines in the world are the Columbian ones (they are on the eastern side of the Andes mountain range). Here are mined the most beautiful and valuable emeralds. However the biggest emeralds mine in the world, at least for now, is in the Brazilian state of Goias (Santa Terezinha). Others important deposits of emeralds are in the Brazilian state of Minas Gerais. These mines are used since the XVI century; as a matter of fact this is the same period when the Egyptian mines, the oldest ones, were used up. More recently, in 1931, a very important deposit of emeralds was discovered in Zambia. Today, in this country there is the second most important emeralds mine in the world.
As stated previously, emeralds usually have many inclusions and fissures; for this reason, cutting this type of stone is very difficult. As consequence, emeralds are typically cut in a rectangular shape with a sort of “steps”. This cut is so distinctive that it is called “step cut” or “emerald cut”. Thanks to this cut, the stone is well protected from the damages of daily use and, above all, its colour, hue and saturation are enhanced. On the contrary, a poor cut makes the gem lacklustre even when it has a good colour.
The emerald is one of the four gemstones which have mostly characterised the history of humanity. The origin of its name probably is the Latin word smaragdus (green stone). In turn, the Latin term has more ancient roots in the Greek language. On the contrary, it is not clear from where the Greek word come from. There are two hypotheses: it could be originated from the Semitic term izmargad or from the Sanskrit word margarda that means exactly “emerald”. However, this stone has certainly and always fascinated the human beings. In fact, the first Egyptian mines date back to 3500 B.C.
The first synthetic emerald was produced and commercialised in the States by C.C.Chatam in 1940. But it was only in 1980s and 1990s when many synthesis techniques were developed. All these methods use the flux and hydrothermal processes and a colourless beryl as base.
Emeralds are really fragile and suffer from high temperatures. This gem is the birthstone of May and the stone used to celebrate the fifty-fifth wedding anniversary.