In March 2018, hundreds of International Gem Society (IGS) members responded to our gem treatment survey. With an abundance of treatments and all-too-infrequent disclosure, this is a subject where many people have strong opinions. We asked whether you consider treated gems natural, what uses are appropriate for treated gems, and how much treated gems should cost. Here are your responses.
By Addison Rice 7 minute read
gem treatment survey results - leaded glass ruby - blue flash off fissues and air bubbles

Leaded glass in this ruby shows as air bubbles and blue flashes along fissures. Due to the invasive treatment, some prefer to call leaded glass rubies “hybrid” stones. © Stone Group Laboratories. Used with permission.

Gem Treatment Survey Methodology

This survey addressed twelve types of gem treatments. For each treatment, respondents read a brief description of the treatment prior to answering questions. There were three questions for each treatment:

  • Is a gem that undergoes this treatment still natural, or is it no longer natural after this treatment?
  • Are these gems appropriate for museums, gem collections, fine jewelry, or inexpensive jewelry? (Respondents could choose multiple answers or none)
  • If an untreated gem cost $100, how much would you pay for a treated gem of the same quality?

In addition, a comment box was provided for each gem treatment.

Who Took the Gem Treatment Survey?

We asked who people were in relation to the gem trade, allowing for people to choose multiple categories. The chart below shows the results. Of the 342 respondents, 149 identified as gem hobbyists, the largest group. Forty respondents chose “Other,” including online retailers, wholesale dealers, and students learning more about gems.

gem treatment survey results - who took the survey

This chart shows a count of each response. The survey allowed for multiple responses.

For certain insights in this article, respondents were grouped into people “in the trade,” anyone who chose Gemologist, Jeweler, Lapidary, Miner, and certain “Other” responses (198 total), and those who are primarily on the buying end of the trade (144).

Treated Gems: Natural or Not?

While most respondents consider low temperature heat treated gems natural (72%), many respondents consider gems with other treatments no longer natural. High temperature heat treatment and laser drilling clarity treatment were both considered to result in natural gems by more than half of respondents. A vast majority of respondents (97%) consider reconstituted gems unnatural.

gem treatment survey results - gems are natural chart

A count of responses saying that treated gems are natural. Blue for those in the gem trade, orange for those who are not.

Separating results by whether the respondent is in the trade or not yields an interesting result. While respondents who are primarily consumers, hobbyists, and collectors make up 42% of respondents, they make up only 35-42% of those who consider a gem natural. (Note: this excludes Coatings, Type B Jadeite, and Reconstituted Gems because few (<50) respondents consider these gems to be natural). This shows that gem buyers are more likely to consider treated gems to be unnatural than those within the trade, but by a relatively small amount.  However, this result may be skewed.  Since the survey respondents are IGS members, they likely have more education on gem treatments than the average consumer.

Do Treated Gems Belong in Museums, Collections, and Fine Jewelry?

Surprisingly, whether a respondent believed that a treated gem was  natural or not didn’t correlate directly with appropriate uses for the gem. Although laser-drilled diamonds were considered to be natural by a similar number of people as high-temperature corundum treatments, fewer respondents believed that they would be appropriate for a museum collection. Gem collections elicited a similar response.

These charts show a count of responses for each treatment, separated by whether the respondent considers the gem natural (green) or not (blue).  Note the changing scale on the x-axis.

Gem variety also affected these results. For example, more respondents considered impregnated or stabilized turquoise natural than lattice diffused gems. However, the lattice diffused gems, which include sapphire and sunstone, were considered more appropriate for fine jewelry. Similarly, fewer respondents consider HPHT diamonds to be appropriate for inexpensive jewelry.

One respondent noted that any treated gem could be part of a museum collection to demonstrate gem treatments and their effects. Although most museums don’t do this, it would be an excellent way to educate the public about gem treatments.

How Much Should Treated Gems Cost?

The biggest question in gem treatments is how much a treated gem should cost.

Clearly, based on the wide spread of values, most people don’t know how gem treatments alter cost. For every treatment, responses varied from $100 (same price as an untreated gem of the same quality) to $1 (1% of the price of an untreated gem of the same quality).

gem treatment survey results - treated gem pricing by natural and not natural responses

Box and whisker plot of cost for each treatment, separated by whether the respondent thought the treated gem is natural (green) or not (blue). Not sure how to read this plot? The black line in the middle of the boxes is the median and the box itself shows the middle quartiles. Lines extend past the box to show the range. Diamonds indicate outliers.

Opinions on whether the treated gem remains natural had a large impact on perceived value. For certain treatments, those who believe that treated gems are natural (green) gave median prices above the upper quartile of those who view treated gems as unnatural (blue).

Surprisingly, separating results by those who make their living in the gem trade (green) and those who are primarily on the buying side of the gem trade (blue) shows little difference.

gem treatment survey results - treated gem cost by whether respondent is part of the gem trade

Box and whisker plot of cost for each treatment, separated by whether the respondent is a part of the gem trade (green) or primarily a consumer (blue).

Highlights from the Comment Boxes

Many respondents provided informative and insightful comments that helped improve our understanding of the gem treatment survey results.


A recurring theme is the need for disclosure of gem treatments to customers. Some commenters note, for example, that it’s impossible to tell whether certain stones have undergone heat treatment at low temperatures. Others mention that treatments are infrequently disclosed, especially in inexpensive jewelry. One gemologist commented that when they disclose treatments, customers are usually uninterested and indifferent.

gem treatment survey results- beads

Many reconstituted gems become inexpensive beads, and sellers rarely disclose these treatments. “Bead Stall” by Barbara Samuel. Licensed under CC By 2.0.

Treatment Categories too Broad

Some respondents remarked that the treatment categories in the survey are too broad. For example, bleached pearls are much more widely accepted than dyed agate and would be priced differently. Similarly, oiled emeralds have less of a reduction in price than rubies with leaded glass (grouped under “Clarity Fillings” in this survey). A few commented that the price point would also vary with gem species and size. The difference in price between treated and untreated 1-ct ruby would be smaller than for a 10-ct gem.

Additive Treatments

Some respondents separated “natural” and “not natural” stones by whether the treatment “adds” something to the stone. Additive treatments include fillings for clarity, dyes, polymers for stabilization or reconstitution, and coatings. A few comments noted that these could be called “hybrids.” In other words, nature has produced a stone, and people have added to it to improve its appearance or durability.


Longevity is a concern for certain gem treatments. Dyed or irradiated gems whose color may fade and coatings which can wear off were viewed as less valuable.

gem treatment survey results - Close up - coated pink topaz

A closeup of coated pink topaz.  Coatings can wear off over time, a cause for concern among survey takers. © Stone Group Laboratories. Used with permission.

More Topics to Include for Next Time

A few comments suggested that the survey should have included assembled stones (doublets and triplets). One mentioned that the survey could also ask about synthetic stones.

A Variety of Opinions

Opinions on gem treatments vary widely. Some respondents believe that any alteration makes a stone “unnatural.” A few even claim they wouldn’t knowingly purchase any treated stone. Others say that anything that miners have pulled from the earth is natural, regardless of how humans have altered it. Yet another group suggests that enhanced stones occupy a realm between natural and unnatural that should have its own category. Others say that there is indeed a line between natural and not, but identifying where the line should be is quite a difficult task. Still other respondents seek out gems for aesthetic reasons and are happy as long as there’s full disclosure.

gemstone treatment survey results - HPHT pink diamond

One collector mentioned a love of HPHT diamonds, with attractive colors and prices. Another respondent commented that this treatment was borderline between natural and not. © Bar Diamonds USA. Used with permission.

What Should We do With This Information?

Certainly, the gem trade has a problem with disclosure. Many respondents noted that the problem is especially pervasive in the inexpensive jewelry market, where even sellers are often uninformed. However, when dealers disclose treatments, customers are often indifferent.

Adding treated gems to museum collections would be an excellent way to educate the public about gem treatments. Here at IGS, we can use our articles to promote a better understanding of gem treatments, including how common they are and how they affect pricing.