millionaire square-cut amethystmillionaire square-cut amethyst

How Can Gem Buyers Protect Themselves from Fraud?

How can gem buyers avoid undisclosed gem treatments and substitutions? Learn why it's best to deal with expert gem cutters rather than commercial dealers.

5 Minute Read

HomeLearning CenterGemologyGemstone TreatmentsHow Can Gem Buyers Protect Themselves from Fraud?
Two major problems plague the cut gemstone market: undisclosed gem treatments and enhancements and substitutions of synthetic for natural gems. Gem buyers need to know these practices occur every day. They must learn how to protect themselves from fraud.
millionaire square-cut amethyst
5.80-ct amethyst, "millionaire square" cut, Brazil. Photo courtesy of and Jasper52.

How Widespread is Fraud in the Gem World?

Most cut gems found for sale have been treated in some way. This is common practice. However, the gem industry often doesn't share that information with consumers. If revealed up front and prices adjusted, treatments shouldn't pose a problem for gem buyers. If not disclosed, however, there is a problem.

Depending on the gemstone type, 80% or more of the cut stones on the market are synthetic but sold as natural. These include amethyst, citrine, morganite, emerald, aquamarine, sapphire, and, especially, ruby, just to name a few of the most popular.

Advice For Gem Buyers

Since trade groups and "watch dogs" seldom enforce regulations, gem buyers must take a "buyer beware" approach. If you're buying gemstones, follow these two recommendations:

Unfortunately, finding "honest" and "experienced" dealers in the gem trade these days is difficult. Look for references, business records, and reviews. Personally, I admit I'm biased and prefer working with reputable gem dealers in the United States. Here, you have more disclosure, safeguards, and ways to resolve problems. However, you'll find both honest and dishonest dealers in the US and around the world. (Otherwise, I wouldn't have written this article).

Finding a gem dealer who actually cuts stones is critical. Most commercial gem dealers have no idea how to cut stones. They buy and resell gems already cut from major cutting centers like Brazil, India, Sri Lanka, and Thailand. Most treatments, substitutions, and just plain frauds happen in and around these centers after or during gem cutting. So, dealers who buy cut stones place a great deal of trust in their suppliers.

I know cutting houses that regularly cut hundreds of thousands of carats of synthetic material. Of course, they sell some of that disclosed as synthetic. However, some houses also mix synthetic with natural material in parcels and sell them as natural to the unsuspecting public. As the stones change hands, no one can guarantee anything, no matter what the original cutting house disclosed. One vendor buys the gems, mixes them, and sells them to the next, usually smaller, dealer. In turn, that dealer sells to a jewelry maker, customer, etc. At that point, who knows a stone's true identity, origin, and treatment?

Why Most Gems are Treated After Cutting

No one is perfect. Treated and substituted stones can slip by experienced dealers, too. However, if you buy from honest gem dealers who actually handle rough and cut their own stones, you'll avoid 95% of the fraud that occurs at the major cutting centers. Why? Because most treatments and substitutions happen after the cut.

But why do most treatments occur after cutting? Can't gems also receive treatments while rough?

Heat Treatments

For heat treatments, the gemstones must be clean. Flaws left in the stone will almost always get worse when heated. In short, most stones must be cut before heating. However, in some cases, gem rough is heated before cutting. Notable examples include aquamarine and sometimes tourmaline.

Experienced dealers and cutters can easily spot heating in rough, so a gem cutter working from rough will likely use untreated stones.

Radiation Treatments

In radiation treatments, small containers of stones are placed in or near a nuclear reactor. Those conducting the procedure almost always irradiate cut stones because they can get many more pieces in the container per run (about 5x more). Each run costs time and money, so you can easily see the motivation for this.

There are very few exceptions. Rough/sawed blue topaz and occasionally rough heliodor are irradiated for the commercial market.

(Editor's note: Bear and Cara Williams of Stone Group Labs have provided some additional information on the topic of modern radiation treatments:

Radiation treatments don't occur near nuclear reactors. Modern treatment facilities run materials by a cobalt-60 (gamma source) on conveyor belts. Charges are often by the ton, hence you see materials such as inexpensive topaz (blue) and quartz (prasiolite) treated in this manner. Typically, this does occur after cutting to reduce weight.)

Gemstone Substitutions

In most cases, expert gemologists can run lab tests to identify synthetics substituted for cut natural gems. Experts can generally easily spot synthetic rough.

gem buyers - synthetic rough
Synthetic rough amethyst

For example, the quartz gemstone family (amethyst, ametrine, citrine, etc) is probably the most substituted material in the cut stone market. Experts have many ways to tell if dishonest dealers switched synthetic quartz for natural rough. They can look at growth lines, color, shape, and so on.

Look at the natural Uruguayan amethysts pictured below. You can't fake those natural crystal points. This rule has very few exceptions. This applies to just about any crystal, no matter what type of rough. So, if a gem cutter cuts a stone with a natural point, gem buyers should have little doubt the stone is natural.

gem buyers - natural rough
Natural rough amethyst

Once cut, synthetic quartz becomes harder, if not impossible, to catch. This is true for most gemstones. Cutting makes it harder to distinguish synthetic from natural. Thus, most substitutions involve cut stones.

Testing Cut Gems for Substitutions

Now, gem buyers have another reason to go with reputable gem cutters who purchase and handle their own rough. These experts can test their rough and identify synthetics before cutting. Cut stone dealers have to rely on what their suppliers tell them. Without conducting fairly expensive lab tests on the cut stones in question, they're in the dark.

Unless the dealers or gem buyers pay for the tests, there's no way to be sure if a commercially cut stone is natural.

The concerned parties will usually test expensive stones. However, the tests themselves may cost more than less expensive stones, like quartz. Since these stones seldom merit testing due to cost, unscrupulous dealers often substitute synthetic quartz gems for naturals in the cut stone market.

Questions Gem Buyers Should Ask

Is the Stone Natural or Synthetic?

You can encounter substitutions in just about any store. This is always a good question to ask.

What is the Stone's Clarity?

I would only recommend stones with clarity grades ranging from IF (free of inclusions) to VS (very small inclusions). Be aware of different and sometimes misleading grading systems.

Is the Stone Heated?

Heating is a very common treatment for many gem types. It can lighten color or eliminate unwanted secondary colors or tones. Personally, I have no problem with disclosed heating. Heat only modifies a stone. It doesn't put something into the stone that wasn't already there. However, some purist gem buyers only want "unaltered" stones.

Is the Stone Irradiated?

Some commercial stones are irradiated to alter or add color. Personally, I don't like adding things to stones that weren't there before. I don't recommend irradiated gems.

The Bottom Line

Gem buyers, you get what you pay for. You want to deal with expert, honest, experienced gem dealers who cut their own rough. However, they cost more, so you must decide if it's worth it.

gem buyers - cut synthetic amethyst
Synthetic amethyst. Photo by Mauro Cateb. Licensed under CC By 2.0.

Jeff R. Graham

The late Jeff Graham was a prolific faceter, creator of many original faceting designs, and the author of several highly-regarded instructional faceting books such as Gram Faceting Designs.

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