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Currently, there are two principal methods of permanently changing the color of a diamond:
♦ Irradiation + Heating
♦ High Pressure High Temperature Heat Treatment (HPHT treatment)
Both of these treatment processes are considered legitimate as long as they're disclosed to buyers. Unfortunately, some people try to pass off treated diamonds as naturally colored in order to get a higher price. So before investing a high sum of money in a fancy-color diamond, have the stone tested by a reputable gem laboratory for possible color treatment. Also have the seller write on the receipt that the diamond is natural and not treated. There's nothing wrong with color treatments as long as you are told about them and not charged natural color prices.
Not all diamond color treatments are permanent and legitimate. Many are temporary and done only with the intention of deceiving the buyer. Occasionally the girdle or back of the diamond is coated with a chemical or plastic to make it look less yellow. Sometimes bits of carbon paper under the prongs or a few dots of ink on the girdle are used to improve the color. In one instance a 9 1/2 carat fancy pink diamond at a major auction house was switched and replaced with a stone coated with pink nail polish. To avoid these deceptive tricks, deal with reputable jewelers.
Why Color-Treated Diamonds Aren't as Well Accepted as Other Treated Gems?
Most rubies and sapphires are heat treated at high temperatures to improve their color, and this is considered a standard trade practice. Red tourmaline is commonly irradiated to intensify its color, and this is also considered normal. Color-treated diamonds, however, are not as well accepted. Three reasons for this are:
♦ Unlike many other gems, there's an ample supply of attractive, untreated diamonds.
♦ Diamonds cost a lot more than most other gems, so more money is at stake. When the prices of rubies and sapphires approach those of top quality diamonds, high-temperature heat treatment becomes less acceptable.
♦ Unlike colored-gem dealers, most diamond dealers don't stock color-treated stones, so they view them as a threat to their business. Treatments are not always disclosed; treated gems confuse consumers, and they can reduce the price of natural-color gems.
A good example of this occurred in the mid- to late- 1970's. Thailand began heat treating low-grade Sri Lankan sapphire on a large scale and the treatment was not disclosed to buyers. Prices of natural-color sapphires dropped when they had to compete with treated stones, which had better color and clarity. So far, color treatments have not affected the prices of natural diamonds. Fancy color diamonds are worth far more than their treated counterparts. A $2000, irradiated green diamond might sell for over $200,000 if it were natural. Prices of high-pressure high-temperature treated diamonds (HPHT-treated diamonds) have not been established yet because they 're relatively new.
The colorless type were first introduced to the trade in 1999. Trade magazines have stated they're being sold to jewelers for about 15 % less than natural-color diamonds. This is high considering that these treated diamonds are produced from brown diamonds. But as more HPHT-treated diamonds enter the market and competition increases, prices for them will most likely decrease.
HPHT-treated yellowish-green diamonds were introduced at the beginning of 2000. In October 2000, the trade press announced that the General Electric Company was able to produce HPHT blue and pink diamonds. The producers will naturally try to get the highest price possible for these diamonds. They claim their treatment process is as natural as the process of cutting and polishing a diamond and that it's just an extension of the high temperatures diamonds are exposed to when formed naturally.
Gems are also subjected to radiation in nature, but the trade does not view irradiation treatment as a natural process. According to Arthur Langerman, a Belgium dealer who specializes in colored diamonds, irradiated and heat-treated diamonds just imitate the real thing. He says that treated diamonds have a value to the people who sell them but not to the rest of the trade. To illustrate this, he said that he'd received a few irradiated diamonds instead of payment a few years ago. He still has them because he hasn't found anyone who wants to buy them. Auction houses wouldn't even take them for zero.
Langerman poses the question, "If you have $100,000 to spend, what would you buy a natural white diamond or a diamond that has been artificially treated.