Emerald is a type of the natural material beryl, colored green because of small amount of chromium and vanadium. It is greatly valued as a gemstone and by weight is the most precious gemstone in the world, even though it is frequently prized less because of inclusions, which all emeralds have to some extent. Beryl is one of the hardest natural materials and has a hardness of 7.5 - 8 on the 10 point Mohs scale of hardness. On the other hand, the efficient hardness of an emerald is regularly decreased by fissures and inclusions. Most emeralds are very much included, so the rigidity (strength not to be broken) is characterized in general as poor.
Emeralds occur in many hues of green and bluish green. There is a broad range of transparency, dependent on the inclusions and cracks in the crystal. Pure minerals with dark yet bright color demand the highest costs.
 Most emeralds are oiled because of the post faceting procedure, in order to advance their clearness. Cedar oil is regularly applied, as it has the same index of refraction, and it is a normally recognized practice. The Federal Trade Commission requests the revelation of this kind of processing when a steeped emerald is sold. The quantity of oil penetrating an emerald microfissure is very small. The application of green tinted oil is commonly not regarded as appropriate by the gem trade.
Emeralds in ancient times were quarried by the Egyptians and in Austria, as well as Swat in northern Pakistan.
The sparkling brightness of its color turns the emerald into an exclusive precious stone. Nevertheless, actually first-class quality is quite rare, with impurities frequently blemishing the constancy of the color – marks of the chaotic origin which has characterized this gem. Some invisible impurities, on the other hand, do not in any way reduce the high value in which it is considered. Quite the opposite: even with impurities, an emerald in a dense, sparkling green still has a much higher cost than a more or less unblemished emerald whose color is not so deep. Lovingly, and somewhat poetically, the professionals call the plentiful crystal impurities, fractures or fissures which are characteristic of the gem 'jardin'. They consider the affectionate small green plants in the emerald garden as attributes of the uniqueness of a gem which has grown in nature.
Emeralds have been kept in high respect since antiquity. Therefore, some of the most celebrated emeralds could be observed in museums and exhibitions. The New York Museum of Natural History, for instance, demonstrates a cup enchased with clear emerald which pertained to the Emperor Jehangir; this cup is displayed next to the 'Patricia', one of the biggest Colombian emerald crystals, which weighs 632 carats. The collection of the Bank of Bogotá consists of five precious emerald crystals with weights of between 220 and 1796 carats, and marvelous emeralds as well are held in the Iranian National Treasury, decorating, for instance, the tiara of the previous Empress Farah. The Turkish sultans adored emeralds as well. In Istanbul's Topkapi Palace there are displays with pieces of jewels, writing-implements and poniards, all generously decorated with emeralds and other gemstones.
The Green is a Color of Nature and Emerald.
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