Understanding Gem Synthetics, Treatments, And Imitations, Part 1: An Introduction

Tech advances and market forces make it essential for gem buyers to know the science behind synthetic gemstones and gem formation. Learn the basics here.

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Editor's Note: Synthetic gemstones have been on the marketplace for over a century. Today, however, technological innovations and economic forces behoove gem buyers to gain a basic understanding of the science of gemstones and gem formation. This five-part series of articles, "Understanding Gem Synthetics, Treatments, and Imitations," is a chapter from Dr. Joel Arem's forthcoming book, Gems and Jewelry, 3rd Edition. © Joel E. Arem 2011-2013. The International Gem Society (IGS) gratefully thanks Dr. Arem for his contributions to the field of gemology and for allowing us to reproduce this chapter.

Shopping for jewelry is no longer a simple and straightforward adventure. The buyer is faced with a plethora of choices in the form of materials that never existed before, materials that are natural and unmodified, and ones (both natural and human-made) that have been treated and altered in myriad ways. Sometimes the history of the object being offered for sale is revealed to the buyer. Often it is not.

Shoppers everywhere are probably familiar with the phrase caveat emptor - a Latin expression meaning "buyer beware." I suggest that a new expression should become more appropriate for the modern gem and jewelry marketplace: esse conscius emptor - "buyer BE AWARE!" It is no exaggeration to suggest that the proliferation of gemstone treatments and the flood of imitation and synthetic gems offer the most formidable challenge to its image and integrity ever faced by the gem and jewelry trade.

One of most well known varieties of synthetic gemstones, cubic zirconia may look like a diamond but has a distinct chemistry and physical structure.
One of most well known varieties of synthetic gemstones, cubic zirconia may look like a diamond but has a distinct chemistry and physical structure. "Synthetic Cubic Zirconia" by Mauro Cateb is licensed under CC By 2.0

Gemstones have been desired and acquired over the centuries for many different reasons. Primitive people saw in gemstones the embodiment of natural forces that were all-powerful but incomprehensible. To posses such an object might be a way to keep these forces at bay. Ancient civilizations attached magical and mystical powers to gems. Ownership, especially in the form of amulets and talismans, became a path to harnessing and using such powers for personal benefit. Gems were also rare and valuable, and therefore symbols of status and authority, so in every society they became objects of adornment for the influential and wealthy.

Belief in the magical and healing powers of gems appears throughout the world. India, for example, has an ancient and rich literature on the subject, and Chinese culture has embraced the curative power of gemstones for centuries. A modern incarnation is the "crystal consciousness" movement, which has spawned an entire industry devoted to the metaphysical attributes of minerals, gems and crystals.

The rarity of top quality gemstones has made these objects extraordinarily valuable. There are few (if any) other things coveted by mankind that might represent $50 million in value and can be held within a closed adult fist. As portable wealth, gems have enjoyed a unique position in human affairs, and their role as financial objects remains unchallenged. But in all the above cases - as concentrated wealth, as healing objects, as fashion items, as gifts for oneself and others, as "patrimony" (inheritance) and in many other applications - their value is based on the fact that gems are extremely rare natural materials.

This value, of course, has inspired heroic efforts at mimicry. People have, for millennia, used glass and other materials to imitate gems. Serendipitous accidents in ancient times also revealed the fact that certain stones change color when heated. Knowledge gleaned in accidents was eventually harnessed, and gemstone "treatment" (i.e., producing some kind of artificially induced change) became a reality. Some materials, such as blue and colorless zircon, would not even exist if not for heating.

Other changes, such as removing the yellow from blue-green aquamarine to reduce or eliminate the green component, or the production of a uniform rich blue color in otherwise intensely pleochroic tanzanite, are done routinely and accepted by the marketplace without fuss. Other forms of treatment are much less benign.

As technology has improved, methods for manipulating, altering and imitating gemstones have become alarmingly sophisticated. Laboratories and factories also now manufacture a bewildering variety of chemicals that can be produced in the form of transparent crystals. Some of these have the same composition and properties as natural stones, and many do not. Efforts are constantly being made to improve the techniques for growing crystals of materials that duplicate the chemistry, structure, and properties of naturally occurring gem materials.

In times past, all gems were assumed to be natural (having been dug out of the ground and fashioned in some way to enhance their appearance, such as carving, faceting, polishing, etc.), and only a few materials were known to be heated. Glass and other simulants had been around for millennia and were easily detected and identified, despite the fact that gemology as a discipline is only a century old. This simplistic paradigm has vanished.

The combination of treatment, duplication, and imitation has changed the very nature of the gem and jewelry industry. "Natural origin" can no longer be assumed. The production of crystals is a global enterprise, and so laboratories and factories around the world (as well as mines) have to be considered as potential sources for materials that are sold within the gemstone industry. The number and type of such materials are astonishing. Equally amazing (and disturbing) is the number and variety of methods that can be used to change the appearance of both natural and synthetic materials. Heat is still part of the menu. But now the gemstone treatment kitchen uses irradiation, diffusion, and many other techniques to expand the palette of objects that are eventually set in metal and sold in jewelry stores. New methods and materials are coming into the marketplace all the time, and the jewelry industry, mired in tradition and slow to change, simply cannot keep up.

You can't get what you want unless you know what you are getting, and in many cases a seller doesn't even know what has been done to a particular stone or exactly where it comes from. Few jewelers have scientific backgrounds, but science is the core of the problem. And the problem itself can be summed up in a single word: disclosure.

There is nothing inherently wrong with selling pretty cut stones composed of materials that were created in a factory or laboratory. There is nothing inherently bad about altering the color and appearance of any kind of jewelry stone, whether natural or manufactured. Treatment often improves the appearance of natural stones that, because of imperfections or poor color, would otherwise be difficult to sell. These human-made and treated materials offer the marketplace an enormous range of products. All of these products have a place in the market, at prices commensurate with their beauty, scarcity, and demand. The gem and jewelry buyer now has many more choices than existed a few decades ago and can select a product that is exactly suited to the intent of a purchase. It is potentially a buyer's dream come true. Unfortunately, the dream has turned into a nightmare.

What good is acquiring something for a specific purpose if you don't know what you are buying? How can you evaluate the proper cost of an item, or compare the costs of different items, if everything is mislabeled?

It is certainly not the intention of the jewelry market to misrepresent its products. The essence of the problem involves missing information, and can be identified with a particular phrase: chain of custody. The items in a store typically traveled a long and circuitous path before ending up in a showcase. Jewelers and gemstone dealers may not know all the stops made along the way by the products they are selling. Was a stone heated right at the source? Could a gemstone have been treated immediately after cutting? Is a particular stone in a parcel natural (mined from the ground) or created in a laboratory? By the time an item has changed hands several times this vital information has often been lost - or sometimes deliberately obscured. The future of the gemstone trade may therefore depend on a seller's ability to provide a "pedigree" from everyone who has handled a product, starting at its point of origin.

Gemstones that can be guaranteed as natural (mined) and unmodified in any way will certainly have a special market niche, one that I have long referred to as "the organic food section of the gemstone supermarket." The growth of this niche is indeed likely to parallel that of organic foods and become a huge and important product category. The issue of chain of custody has thus far only been seen publicly in the case of "blood diamonds." People around the world expressed outrage over the atrocities committed to acquire diamonds that are used to fund armed resistance movements in African countries. The jewelry trade responded to this negativity by creating a forum known as the Kimberley Process, an affiliation of people and organizations whose goal is to enhance the chain of custody of rough diamonds and make everyone in the marketplace accountable for the source of the stones they sell. This admirable intention is stymied by rampant smuggling and the great difficulty in identifying where a diamond came from by just looking at the stone itself.

In the case of all other gemstones, there is nothing whatever at work that is comparable to the Kimberley Process. The chain of custody is almost universally unsupported by any assumption of responsibility. As long as this situation persists, it will be up to the end user - the gem and jewelry customer - to demand relevant information. Esse conscius emptor - the buyer MUST become aware of the nature and extent of the problem. If you don't know about gemstone treatments and manufactured stones, you cannot ask the critical questions that will enable you to avoid the (mostly unintentional) misrepresentation that pervades the gem and jewelry industry.

The following is an attempt to compress a staggering amount of information into a manageable and readable summary. In order to understand and learn about this subject, we must deal with terminology. Labeling has become a part of the problem instead of a solution. There is little advantage in trying to compress, into a single word or phrase, detailed information that can only be properly understood with a simple, but somewhat longer, explanation.

Basic Terminology

A gemstone is defined as a mineral that is cut and polished for ornamental purposes. Attributes, such as "hard," "durable," "beautiful," and "rare" CANNOT be used to define anything, but only to describe. A definition MUST be unambiguous and non-subjective. There are about 400 minerals that have been cut and polished for one reason or another, including adornment, investment, collections … and even curiosity! Some of these are hard and durable. Many are extremely soft and fragile. Some are rare and some are extremely abundant. Many are beautiful and many are drab or nondescript. But these descriptions merely categorize - they do not serve to tell us what something IS.

A mineral is defined as a naturally occurring element or compound that has a definite crystalline structure and a composition that varies within specified limits.

Anything called a "gem," with no modifying adjectives, must be a mineral (or one of the few historically validated exceptions discussed earlier, such as amber, coral, pearl, etc). The use of the term "gem" in the marketplace has been expanded in recent years to include materials that are not minerals. In all such cases, a qualifying adjective is required to provide a full description. Thus we have such terms as "synthetic gem," "imitation gem," "simulated gem," "treated gem," and so on. A polished stone that is simply labeled "gemstone" must therefore be a naturally occurring, unenhanced, and untreated material or it is being misrepresented.

Gemstones are bought and sold in a global marketplace that is ancient and ubiquitous, steeped in traditions and customs, and even has its own language. Unfortunately, this language has evolved from circumstances having to do with buying and selling products. Words and phrases such as "sparkle," "dazzling," "fine color," and "top gem quality" are not scientific but rather try to capitalize on the "romance" of gems and jewelry and their universally admired history and lore. When language that is intentionally nebulous, suggestive, and flowery meets the necessarily precise and rigorous terminology demanded by science, a battle ensues. This conflict cannot produce either winners or losers - only frustration and endless debates.

The situation is made even more difficult by competition between groups within the jewelry industry, each with its own ideas about "what to call things." Some groups, including appraisers, gem scientists, and professional gemologists push an agenda that relies on terminology that is more acceptable to other scientific disciplines. The market-oriented groups (and there are many) lean towards a "kinder" language ("faux" instead of "fake," "cultured" instead of "synthetic," etc.) that is much less precise but which is viewed as less "damaging" to seller-oriented product imagery. These approaches are diametrically opposed, but all agree that a compromise must be reached. The compromise has become an attempt to conjure up single words or specific phrases that everyone agrees will serve to fully describe any particular type of product that is being offered for sale.

Some synthetic gemstones are clearly labeled as such. Dangers arise for gem buyers when gems are labeled incorrectly in the marketplace, whether in error or deliberately.
Some synthetic gemstones are clearly labeled as such. Risks arise for gem buyers when gems are labeled incorrectly in the marketplace, whether in error or deliberately. "Ruby (Fake)" by maicos is licensed under CC By 2.0

This approach is doomed to fail, mainly because the use of abbreviated and simplistic terminology incorrectly assumes a prior level of knowledge in the hands of consumers, one that is sufficient to make the chosen oversimplified terminology comprehensible. A MUCH more efficient way to deal with the problem is to simply explain to the customer where the product comes from and what has been done to it on its way from origin to consumer. Unfortunately this often requires a level of scientific awareness that is not readily found in the retail marketplace.

This marketplace is therefore steadily and relentlessly burdened with more and more products that are mislabeled, misidentified and misrepresented, while an endless and futile debate over "words" goes on and on within the trade organizations. Everyone loses. The job of "educating the public" about these products is viewed by many gemologists and jewelers as either extremely daunting or simply impossible. Why?

Gem materials are treated, assembled, and manufactured in many ways. There is a lot of information in the upcoming pages. It may be tempting to skip over it and deal with it some other time. After all, learning about all the pretty stones is fun and easy, and the knowledge will definitely enhance your shopping experience. But as soon as your wallet emerges and a sale begins, you have a problem because you might not be getting what you think you are buying, and the salesperson may not be aware of this discrepancy either. So it is up to you to bring enlightenment to all concerned, and have the satisfaction that comes from knowing you are in control of a tricky and awkward situation.


A natural gemstone is one that has emerged from the ground without any processing other than lapidary (cutting and polishing). Treatment is anything done to alter the appearance or properties of a material (natural or otherwise).

A gemstone or other material may be enhanced, i.e. treated, i.e. processed in a way that improves its appearance. Other terms, such as "modified," "improved," "purified," etc., all mean essentially the same thing. Heating is one such process and has been used for centuries to change the color of various materials. Dyes are routinely used to add color in cases where a material is either porous or has networks of microscopic cracks and channels into which vapors, colored liquids, or even melted glass can penetrate. In recent times, radiation has also been used to modify the internal structure of materials and create what are called "color centers." Also recent is the perfection of the process of diffusion, which is the forced penetration of a coloring agent directly into the crystal structure of a solid material. In this case the colorant does not enter via cracks or channels, but moves through the structure on an atomic scale.

It is important to clarify the terminology associated with laboratory-produced gemstones since some confusion exists in the literature. The International Committee on Technical Terminology (ICTT) in 1974, after three years of meetings and deliberations, proposed the following definitions:

  • Synthetic (n.) A human-produced chemical compound or material formed by processes that combine separate elements or constituents so as to create a coherent whole; a product so formed.
  • Synthetic (adj.) Pertaining to, involving, or of the nature of synthesis; produced by synthesis; especially not of natural origin.
  • Homocreate (n.) A human-produced substance (solid, liquid, or gas) whose chemical and physical properties are within the range of those possessed by the specific variety of the natural substance that the homocreate is intended to duplicate.
  • Homocreate (adj.) Synthetic and possessing chemical and physical properties that are essentially the same as those of its natural counterpart; created the same as.

A substance such as emerald, made in the laboratory, is a homocreate. Its properties are specifically designed to resemble those of the equivalent substance produced by nature. However, cubic zirconia, GGG, and YAG are true synthetics - simply compounds made in the laboratory, assembled from components. They have no natural counterparts and are used as gemstones based on their own meritorious properties. In other words, all homocreate materials are synthetic; but not all synthetics are homocreate.*

A synthetic material is one that has been created or manufactured by humans and therefore represents the antithesis of "natural origin." The word synthetic itself derives from Greek, meaning "put together," i.e. by intent. The phrase "synthetic mineral" is therefore actually a contradiction in terms. Scientists have avoided this dilemma by creating better descriptive words. One such is homocreate, which is a manufactured product that has the properties of a naturally occurring material. Alas, the gemstone field has never accepted or used this term. We also encounter phrases like "synthetic gemstone," which does have the benefit of the preceding adjective that is required to modify an otherwise precisely defined word. Other phrases, such as "lab grown," "man-made," etc. are all different ways of saying the same thing. Another popular marketing term is cultured, which somehow implies sophistication, but in the case of most gems is just another way of saying "synthetic."  In the pearl market, however, "cultured" has an entirely different meaning. Cultured pearls are indeed pearls made by shelled animals, but the process is initiated by human intervention. In most cases this involves the insertion of a "nucleus" of some kind, around which the animal creates layers of nacre that eventually build up to produce the object that is harvested for use in jewelry.

The term artificial specifically refers to something that is made by humans. The word itself is derived from Latin words for "to make" and "skill". An artificial gemstone is something that is made to look like a gem and could be composed of any suitable material (glass, plastic, synthetic crystal, etc.). A simulant (from a Latin root meaning "copy") is something that is intended to appear to be something different.

These definitions were unanimously approved by the ICTT and have been adopted by most professional scientific societies. If gemology is ever to consider itself a true science, it will only do so if it begins to walk in step with other disciplines having a much longer history of empirical and theoretical evolution.

A simulated gemstone could be made of any suitable material, whether natural or synthetic. Its intent is mimicry. A "simulated ruby" might be red glass, red plastic, a red synthetic crystal, or even a natural red garnet or spinel! A less popular but equally accurate word for this would be imitation, or the much more popular version "faux" (fake).

The word "real" means "in a state of actual existence," as opposed to something that is thought or appears to exist. A "real gemstone" is something that merely has an objective existence in the physical universe. If it is not natural in origin and is sold as a gemstone, it is misrepresented, unless described with a suitable adjective (e.g. synthetic, simulated, etc.). Something that is "genuine" means "having the attributes and properties that are claimed for it," which of course does not mean the object is natural. A "genuine synthetic emerald" is authentically synthetic, but if a man-made stone is marketed as "genuine emerald" without the modifying adjective, we have a case of misrepresentation. The word authentic does not imply natural origin, any more than "genuine."

A new and troubling material, widely sold without disclosure, is a blend of red-colored glass and bits of natural (low grade) ruby that have been melted together. The final product can be quite transparent and attractive and is often marketed simply as "ruby." The exact mix varies but can be as much as 50% (or more) glass. Nobody knows what to call this stuff. It does have natural ruby (red corundum) in it, but there is often too much glass present for it to be simply called "treated ruby." Some gemologists advocate the word "hybrid." Others like the phrase "assembled," and still others "composite." There is a lively debate over what single word or phrase is most appropriate to use when selling this material, even though a single word obviously cannot suffice. Perhaps the best descriptor is "red corundum glop," but this term has not yet been seriously advocated.

Another troubling aspect of selling this ruby-glass mixture, fraud notwithstanding, is the fact that the glass can be degraded even by household cleaners, and may even turn white when exposed to liquids as ordinary as lemon juice. Lead glass-filled "rubies" are also subject to falling apart when placed in some of the acid solutions that are typically used in cleaning metal jewelry. Needless to say, these circumstances would be disturbing to both the person doing the cleaning and the owner of the so-called "ruby!"

None of the single words being debated within the gemstone trade completely and accurately describe this material. It seems much easier to simply explain what it is, as above, so buyers can then translate into an appropriate image ANY of the marketing terms that gemologists and sellers decide to use. Basic education totally avoids the illusory "problem" of having to come up with single all-inclusive word to describe something that defies this kind of simplistic approach. But the problem of educating the mass-market sufficiently to achieve this goal remains a perceived immovable barrier within the gem and jewelry industry. This perception cannot be correct.

* A Note From Donald Clark: Dr. Arem's article, "Understanding Gem Synthetics, Treatments, and Imitations," is a wonderful piece.  I have a great deal of respect for Dr. Arem. His Color Encyclopedia of Gemstones is the best reference of its type. He once helped me with a difficult identification. I didn't expect a personal letter from him and was pleased that he would go out of his way to help me. This was before the existence of the IGS.  However, you should be aware that he defines the words "synthetic" and "homocreate" in a manner inconsistent with our industry standards. In my article, "How Gems Are Classified," I define "synthetic" as "materials that duplicate their natural counterparts" and "homocreate" as materials that have "no counterpart in nature," in accordance with the Gemological Institute of America (GIA).

Understanding Gem Synthetics, Treatments, And Imitations, Part 1: An Introduction

Understanding Gem Synthetics, Treatments, And Imitations, Part 2: Crystal Growth

Understanding Gem Synthetics, Treatments, And Imitations, Part 3: Synthetic Diamond

Understanding Gem Synthetics, Treatments, And Imitations, Part 4: Synthetic Gemstone Guide

Understanding Gem Synthetics, Treatments, And Imitations, Part 5: Identifying Gemstone Treatments

Joel E. Arem, Ph.D., FGA

Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.

Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. joelarem.com

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