Oiling is a gemstone enhancement commonly used with emeralds which have many natual fractures and fissures within it's structure. The oiling of emeralds is considered standard operating procedure; only the rarest, finest emeralds do not have any surface fissures that will keep oil from penetrating it's interior. Immediately after mining, rough emerald crystals are thrown into a barrel of oil to absorb the substance, and oil is used during the cutting and polishing process as well.
See Also: Enhancements, Anneal, Glass Filled