If you shop for bargains in gemstones online, one of the first things you’ll notice is that most of the stones have been treated or enhanced in some way — with heat or chemicals or radiation or some combination. Are these treated stones really a bargain? Or are you better off spending more, and getting a truly “natural” gem?

One Answer

Here is one answer to the question. Gemstones are a wondrous product of nature, and their natural beauty should not be enhanced or “improved” in any way. If you don’t care about buying a truly natural product, you can buy a synthetic or fake or “treated” gemstone. But only nature can produce a true ruby or sapphire.

I am sure many people would agree with this point of view. But it is actually quite naive if you think about it. After all, you don’t see many people wearing unprocessed minerals on their fingers or around their necks. The fact is, people expect that natural minerals will be improved by skillful cutting and polishing. Gems don’t come out of the mine with a facet cut! If you’ve seen rough uncut sapphire, for example, I’m sure you were amazed that a gorgeous blue sapphire could be produced from that clump of dull aluminum oxide crystals.

So as we think about this, we realize that gemstones are a product of human craft worked on natural materials. The question then, is what kinds of enhancement are acceptable? And how do these enhancements affect the price and value of a gemstone?

In this article, we focus on the most common form of gem enhancement — heat treatment. Look for an explanation of other treatment methods in our next article.

Why Gems are Treated

Some gemstones, such as garnet and peridot, are hardly ever treated. Others, like ruby and sapphire, are routinely treated. Why is that? And why are treated rubies so much more expensive than untreated garnets?

Some highly desirable gems, like ruby and sapphire, are scarce and the supply of high quality stones tends to decline as mines are worked out. At the same time, demand is high and growing. The search for new sources of gem-grade material typically leads to the mining of lower grade gems, as it did in Mong Hsu in Burma in 1992. The Mong Hsu rubies tended to a bluish or purplish hue that was not the wonderful “pigeon’s blood red” that people found so desirable in the Mogok Burmese rubies that were now in very short supply.

Ingenious gem labs in Thailand found that the color of the Mong Hsu rubies could be improved by heating, producing a ruby that had the distinctive Burmese look. This treatment or enhancement is now routine for Mong Hsu rubies, for mid-priced as well as more expensive stones.

Sapphire is another type of gem that is routinely enhanced by heating. Natural sapphires are typically “included” to some degree — that is, they have internal deposits of foreign material or structural irregularities that affect the clarity of the final product. These inclusions often lend a cloudy appearance to the gem. Heating the gem material at high temperatures (over 1000 degree centigrade) can “heal” many of these inclusions, since they have a lower melting point than the sapphire. The result is a clearer gem with a more attractive color.

The value of a gemstone enhanced by heating is, not surprisingly, lower than that of an unenhanced specimen with the same color and clarity. The unenhanced gem, of course, is extremely rare. Without the enhancements produced by heating, the supply of eye-clean ruby and sapphire of good color would be so small that these gems would be available only to a tiny number of well-heeled customers.

Some Practical Advice

As you shop for gems online, look for a “Treatment” section in the description of the gem. If the gem has been heat treated, the seller should disclose that fact. If you are shopping for ruby or sapphire, and the seller claims the stone is unheated, buyer beware! It is entirely possible that you’ve come across a rare untreated gem, but the stone should be priced accordingly. Be very suspicious if the price of the allegedly unheated gem is in the same range as similar gems that have been heat treated.

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