Some of treatment procedures are centuries old, while others are relatively new. Gemstone are treated in different ways to improve their appearance. Some of these procedures are centuries old, while others are relatively new. Also, by cutting or polishing gemstone could have fabulous colors and nice sparkle. Treatment or enhancement gemstones means any process to make natural gems improved gem’s color, clarity before cutting and polishing. Please understand that TREATMENT AND ENHANCEMENT has nothing to do with man created gems or synthetic gems. Treating and enhancing gemstone is a very common step to improve gems appearance. Some treatment and enhancement improved by nature are permanent and cannot be detected. Treatment and enhancement procedure so closely resembles what happens in nature, that one cannot always tell if they have been treated after mining or before. Microscopic examination will sometimes reveal an inclusion that burst during heating treatment, but lacking that there is no way to tell exact that heat treatment was done before or after mining. There are many techniques of treated or enhanced gems (More knowledge at http://www.facedgem.com/gemstone-knowledge/gemstone-treatment.htm). Briefly explanations of the important techniques is given below.

Oiling treatment method has been used form more than hundreds years, mostly emerald treated to derive its beautiful green color and clarity. In the same way, other colored stones such as alexandrite and rubies have been treated this way makes less surface inclusions. So we can concluded that colored oils are used on those gemstone to improve their appearances. This treatment reduces fractures and provide better clarity.

Heat treatment is the most common form and famous enhancement. This is so common with corundum, ruby and sapphire, it is recommended that jewelers inform their customers that they are "probably heat treated". Heating can cause color of a stone to darken, lighten, or even completely changed and can also improve gems clarity and brightness.
Heating of most kinds of gemstones is a standard treatment procedure. Heating knowledge was passed over generations. Heating Methods vary from simply burning method to highly techniques under regulate temperature (More knowledge at http://www.facedgem.com/gemstone-knowledge/gemstone-treatment.htm).

Diffusion is an enhancement method, commonly used on corundum, added iron and titanium during the heating process of the gemstone, sometime called surface diffusion. Diffusion layer created by adding elements. This layer described as colored coating.

Radiation enhancement or irradiation means pounding material with subatomic particles. In some case, irradiation is followed by heating to produce a better or new color for the gem - such as topaz. Today so many irradiation technique applied and has created shades that cannot found in natural topaz. Same way in tourmaline, irradiation can turn dark pink stone into red. For diamonds irradiation and heating can turned them into browns, blues, yellows, pinks and greens.