As they are extracted from rough bare rocks, raw diamonds might not be in shape to be sold in markets just like that. This is why they are treated before they are sent to make jewelry such as a ring made out of the diamond.
In fact, almost all of the organic gemstones are treated before being sold. Below are the most common gemstone treatment methods.
In this kind of treatment, the gemstones are completely immersed in colored or colorless oils. This is done so that they attain the desired durability and appearance.
This process is used mainly for opaque gemstones. It is done to improve the stability and appearance of gemstone that are porous. Wax is used to cover surface cavities and cracks to improve the texture.