What is "oiling treatment" of an emerald?
The term "oiling" regarding to the emerald is a common, acceptable and reversible kind of enhancing of the gem in order to improve the visual performances of the clarity. Oiling is a kind of enhancing that is diagnosed visually. Oiling is the most common type of enhancing the emerald.
This type of enhancing has a number of disadvantages along with advantages:
- enhanced stones require a very neat approach to cleaning since oil is easily removed by many modern detergents;
- enhanced stones are undesirable to heat so oil can escape from cracks on the surface of the stone as a result of thermal expansion;
- oil treated stones must be cleaned from time to time and re-processed as the oil eventually polymerizes and becomes cloudy.
Sometimes emeralds are enhanced in two parameters at once (both in clarity and in color) using colored oil for impregnation. This kind of enhancement is not acceptable as it is often applied to stones that are not emeralds by definition.