Due to the fact that many emeralds contain fractures that reach the surface of the emerald, emeralds are often treated to reduce the visibility of these fractures. One of the oldest and most common treatments for emerald is called oiling. Emerald treaters will force oil into the fractures in an emerald. Filling the fractures in an emerald allows light to pass through the fracture more easily making it less visible much like repairing a crack in a windshield. Filling an emerald with oil is not permanent. The oil can evaporate and discolor, heat can make the oil sweat out of fractures and solvents can dissolve oils. If the oil in an emerald needs to be replaced, the emerald can be soaked in a solvent to remove the old oil and the emerald can then be re oiled. Today emeralds are also treated with manmade resins in much the same way as they are oiled. The resins used to fill the fractures in emeralds are typically more effective and longer lasting than oiling. Some resins may dry out and crack or discolor and it may be impossible to remove the resin in the fractures completely making it impossible to re treat the emerald to make it did after the initial treatment. Due to the potential instability of some treatments it is important to know if your emerald has been treated. A competent jeweler or gemologist should able to tell you if your emerald has been treated but if you know your emerald is treated it is a good idea to a jeweler before allowing them to work on your emerald jewelry.