Emerald Deep green beryl is known as emerald. the name derives from greek smaragdos and means green stone. Emerald is the most precious gem in the beryl group and as such is the most sought after. The coloring agent for real emeralds is chrome but a lesser emerald is coloured by vanaduim although this should be called green beryl but most people still call it emerald.All emeralds are brittle and must be treated with care. Most emeralds are enhanced by oiling which can be done before cutting or after most rough gemstones will be placed in oil to await cutting. It has a mohls hardness of 7.5-8 and a refractive index 1.565-1.602. Found mainly in central america and Africa with the most sought after being from Colombia especially the muzo mine northwest of Bogota. Emeralds have also been found in Russia and other countries but the quaility is lesser than that of cetral america nad africa