The trade of gemstones is phenomenally large, the annual turnover being more than US$50 billion. A major share of this market is in diamonds, as these stones are bought for investment as well as for decorative purposes. The price of a diamond, however, has no relation to the actual cost of production, but lies in its comparative rarity. Over the years, by controlling the quantity of diamonds entering the market, the diamond trading company has kept the price of good quality diamonds stable and at a high level, ensuring its investment value. Sales publicity by jewellers, too, has encouraged a preference for diamonds over that for other gems. Substitutes like cubic zirconia, moissanite and Yttrium Aluminium Garnet (YAG), though equally lustrous and attractive, do not have the same appeal.
Most gemstones, diamonds included, are pale in color, often with inclusions, cracks or voids and since such stones are commonly available, they are cheap and so difficult to sell to discerning buyers. The improvement of the color and the clarity of these low quality stones is therefore of extreme importance to the trade. Research in material science has now given us the ways to improve the appearance of gemstones permanently and there is indeed considerable enhancement in the value of gemstones after treatment. On the other hand, there are people who have voiced serious objections to altering what nature has provided. It is a fact though that man is constantly improving on nature to make profits for himself, whether it is plastic surgery or gemstone enhancement.
There are many techniques used to enhance the color and quality of gemstones. Radiation treatment using gamma rays, electrons, x-rays are few. The most famous method of gemstone treatment is heat treatment. Specially corundums are heat treated to produce bright color blue sapphires. Heat treatment is a very popular method for enhancing colors of sapphires. Heat treatment to standards are accepted by the trade.