Most of the gemstones undergo some treatment to enhance the color and durability. Many treatments alter the color of the stone significantly. Mostly rubies and sapphires are subjected to artificial processes like high temperature heating to alter the color or clarity of these stones. Sometimes foreign substances are included which change the chemical nature of the stone entirely and thus, change the color. Blue topaz is one example which is colorless in its natural form but irradiation and heating changes its color permanently. Citrine, pink topaz, tanzanite are some stones on which treatments are considered acceptable and to keep these stones affordable also, such treatments are necessary. Some treatments are permanent and can not be detected easily. However, there are other treatments which are not too permanent and not stable.

Most common treatments which are given to gemstones are heating, oiling (usually on emeralds), irradiation, dyeing, impregnation (wax infusion), bleaching, coating, diffusion (on sapphires), filling and lasering. Of these, heating is most common treatment given to stones. The color of the stone can be lightened, darkened, or completely changed; can improve the clarity of the stone through the heating treatment. This process is irreversible and can only be detected in laboratories.

Though the resultant stone looks very appealing to the eye in terms of color and clarity it will not be considered truly natural and untouched. Also, it will not count as rare because one can find many such fabricated stones anywhere else. Most natural gemstones are far from beautiful and in fact they undergo treatment to enhance their appearance. Natural, unheated, or untreated gemstones are extremely rare to find and thus they are very highly priced. There are certain stones which are not treated like most Garnets, Peridot, Lolite, Spinel, tourmaline, malachite.

For some people a gemstone in its natural color is a prized possession and most of its appeal lies in the fact that it is not enhanced and untreated. But for many people, price still is the deciding factor and they go for the cheaper stones which mostly are the treated gemstones. There is a market for every kind of stone, treated, imitated, lab created, and natural. Depending on the end use of the gemstone, the buyer should buy the stone. A buyer has the right to know the correct information about the stone. The seller should disclose this information to the buyer at the time of purchase. There are companies which sell truly natural gems with a certificate attached to the stones which authenticate the claim. For collection pieces, one should go for rare and untreated, natural gemstones.