Emerald is a natural benefited stone and represents good fate and fortune, divine guidance, divine grace, education, power of speech and knowledge. Very wide optical transmission band from UV to near-infrared, highly resistant to scratching and abrasion, extremely high melting temperature. Stone emerald belongs to the important group of beryl gemstones. There are quite a few different gemstone-quality varieties of beryl, most of which are classified based on colour and colouring agents, such as pink morganite and red bixbite. There are also many other green coloured gemstones that can be confused with green emerald, including aventurine, demantoid garnet, tsavorite, chrome tourmaline, chrome diopside, grossularite, uvarovite, verdelite, fluorite, hiddenite and peridot. Oiling is a common emerald treatment and in most cases, it is done right at the mining location. The term 'oiling' refers to the practice of immersing emeralds in a colourless oil or resin (most often cedar oil) in order to enhance colour, clarity and stability. Emerald is the most precious stone in the beryl group. The name comes from the old French word 'esmeralda', which was derived from the Greek word 'smaragdos' meaning 'greenstone'. By definition, emerald is any medium to dark green beryl coloured by chromium. Green beryl coloured only by vanadium is not considered to be true emerald, but rather as simply green beryl.