Lead-Glass Filled Ruby:
A Case Study in Misrepresentation and Deception
I find it very disturbing that there are still many people in the gem and jewelry field who do not yet understand how lead-glass “rubies” – now identified by leading gem testing laboratories such as the Gemological Institute of America (GIA) and American Gemological Laboratories (AGL) as artificial products--differ from rubies that are sold, legitimately, as “treated” rubies. Some jewelers and gemologists are even objecting to what the laboratories are calling them and continue to sell them and identify them as "treated rubies." Tragically, because of confusion about what they really are, and how they differ from treated products, these imitators are now flooding the market here and abroad, and selling at greatly inflated prices.
I felt so strongly about the unprecedented issues these lead-glass imitators present, that I added extensive information about them in the latest edition of my book Jewelry & Gems: The Buying Guide (Seventh Edition) and an entire new chapter to the Fifth Edition of Gem Identification Made Easy (which just rolled off press a month ago). Since we are now in a "social media” era, however, let me attempt here to clarify the differences, and why selling lead-glass products as genuine “treated” ruby is misleading and deceptive. It is long for a "blog" but I hope you'll read it through to the end.
As many know, heat treatment of ruby and sapphire has become the norm over the past half century, and this type of treatment is “assumed” when buying most rubies and sapphires today. In more recent years, we’ve also see more extreme levels of heating which require borax coatings, in which the borax can melt and leave “residue” in fissures. We've also seen the introduction of glass-fillings into fractures to reduce their visibility. A few years ago, however, we began to see a new ruby product at gem shows, offered for a few dollars per carat. Most were represented as being “treated by heat only.” It wasn’t long before gemologists discovered this was not the case.
Many gemologists and appraisers began receiving calls from bench jewelers who were finding out – the hard way – that these new “rubies” were not behaving like any ruby they’d ever handled! We began to realize that routine jewelry techniques caused extensive damage that was irreparable! Unlucky bench jewelers who “destroyed” one of these new “ruby” products while doing “routine” jewelry work, suffered damage to their reputations, loss of customers, and were held financially responsible by retailers and/or consumers. This type of reaction at the bench, and the consequences faced by bench jewelers, was unheard of…until the lead-glass “rubies” entered the market.
Gemologists had to ask, what’s different about these? Why don’t they respond as ruby should respond? So beginning several years ago gemologists from the Accredited Gemologists Association (AGA), myself among them, began to purchase stones from various vendors, at various shows, and we undertook research on the stones themselves, as well as how they were being represented and priced.
Gemological examination of the stones revealed unprecedented quantities of glass – a lead-glass in particular – combined with an undeterminable quantity of corundum (the mineral known as ruby only when it occurs in a red color with good transparency, or “sapphire” when it is blue or any other color in which nature creates it); we discovered the "rubies" were actually a “blend” of two materials that are altogether different in terms of physical properties.
The first difference noted was that the glass used in these products was not a “silica” glass – the type of glass used in traditionally “glass filled” rubies – but a formulation of lead glass. The reasons that the producers of this new product would use lead-glass became clear very quickly: lead-glass is essential because it makes it impossible to see where the glass and corundum begin and end! The high “refractive index” (RI) obtained by introducing lead into the glass is virtually identical to the RI of corundum, which means it is impossible to distinguish one from the other. Furthermore, one of the most important tests used to identify any gemstone – using a refractometer to determine a stone's RI – will give the same reading for the lead-glass ruby as for a treated or natural ruby, even if the stone is situated on the refractometer so that the part of the stone being tested is actually glass, RI reading will be the same as that of ruby! (For a full explanation of what RI actually is and why it is so important, see below – What Is RI And How Does It Affect Quality Grading).
Subsequent research by AGA members, in association with several of the world’s leading gem-testing laboratories, revealed that the lead-glass becomes an integral part of the blended product and cannot be removed without destroying the "gem.” This is an important difference between this product and "treated" ruby because the properties of the blended product are no longer the same as the properties of "ruby." The properties are, in fact, very different. This, combined with their inseparability, means the lead-glass “ruby” may look like ruby but it won’t act like ruby!
In addition, the lead-glass component represents a much higher percentage of the stone than what is found in “treated rubies.” The silica glass used in traditional treatment is used simply to reduce the visibility of the fracture(s), and thus, the amount of silica glass used in the treatment of ruby or sapphire is very minimal. Even more important, silica glass has a much lower RI than lead-glass, so the fractures can be seen when the stone is properly examined; silica glass doesn’t “hide” the fractures (and if there were any question, silica glass can be removed without damage to the stone should there be any need to do so, and in the rare case where the glass comes out of the ruby for any reason, it can be re-filled).
These are critical differences between “treated ruby” and the lead-glass products: 1) It is impossible to see where the glass actually is so you cannot determine how much of the stone is glass versus ruby; 2) the two very different materials become inseparable. Without the lead glass, there is no ”ruby” in terms of color and transparency, but with the lead-glass, the physical properties are so altered that the resulting “ruby” lacks the characteristics that make “ruby” a ruby.
The process by which lead-glass ruby is produced requires the fusion of these two very different materials, but the result is something that is no longer ruby nor glass. Instead, the product is a new type of imitation that combines the properties of two very different materials, each inseparable from the other. In short, they are a new type of “composite,” an imitation created from two or more materials being joined together in some way, to imitate a rarer and more costly gem. Composites can be formed from two or more parts of a genuine stone, or two or more parts of an imitation or synthetic, or from a combination of genuine and artificial.
This new product is now being sold as “treated ruby,” at inflated prices, and poses a serious threat to consumers that was unknown at the time of the last FTC review over 10 years ago.
The AGA collected numerous real-life examples of the problems created as a result of selling this product as ruby when the most important physical characteristics associated with ruby—its toughness, hardness, and overall durability, ranking it next to diamond in terms of these characteristics—is not present in this new product; these composites are not only less durable, they are very fragile. For those interested in reading about these specific cases, please go to FTC website to read the attachments to the AGA submission (the first one listed): http://www.ftc.gov/os/comments/jewelryguidesreview/index.shtm
In addition, the lead-glass component has other adverse effects on the ability of anyone selling this product to be in compliance with current FTC guidelines related to: a) identity of the stone; b) carat weight; c) quality; d) disclosure related to care requirements; and e) value.
The lead-glass products now in the market are being misrepresented specifically as to their “type,” “kind,” “quality,” “weight,” “durability,” and “value” as specified by the FTC guides:
- Kind: The lead-glass products are being misrepresented as “treated ruby” when the altered material no longer has the properties of ruby. This lead-glass product is neither ruby nor glass, but a new type of imitation that combines properties of both glass and corundum, each of which is inseparable from the other.
- They have been clearly identified by the two most highly respected gem-testing laboratories in the USA—the Gemological Institute of America (GIA) and American Gemological Laboratories (AGL) as products that are not genuine ruby, treated or otherwise. GIA identifies them as “manufactured products,” and AGL identifies them as “composite ruby.”
- Both labs include comments pertaining to presence of significant amounts of lead-glass, and the need for unusual care. The AGL laboratory states: “the product has been heavily treated using a high refractive index lead-glass to fill fractures and cavities, vastly improving the apparent clarity and adding weight. The glass may be damaged by a variety of solvents.”
- There are devastating consequences resulting from using traditional techniques on these lead-glass “rubies” at the bench—extreme and irreparable damage—not ever associated with any other ruby that has been subjected to any type of treatment, including the use of silica glass to reduce the visibility of fractures, but which is unique to the lead-glass product. Lead-glass products may look like ruby, but they are products that lacks the durability of ruby, a very important characteristic long associated with ruby.
- Quality: Because of the composition of the product, and the extensive amounts of lead-glass, no one can know the true quality of the product because it is impossible to do accurate color and clarity grading—the two most critical factors involved in determining the quality and value of any gemstone. Lead-glass products cannot be accurately graded for 3 primary reasons:
- The high refractive index (RI) of the lead-glass conceals the fissures/fractures, making it impossible to determine how many there are, how deeply they penetrate into the stone, and thus, how great a risk they pose with regard to breakage in the course of normal wear. (See below for an explanation of what the RI is and how it affects quality and clarity grading).
- The filler cannot be removed. Another important distinction between lead-glass fillers and other fillers used routinely to treat ruby/sapphire to improve appearance—and which can rightly be sold as “treated ruby”—is seen in whether or not the filler can be removed for any reason. Other fillers, including common silica glass, oil, or epoxy resins, can be removed in cases where this might be necessary to determine whether or not a coloring agent has been added to the filler, or to ascertain how much filler—how heavily filled—the stone is (as with epoxy resins used in emerald). In the case of the lead-glass filler used in these stones, the lead-glass used to create the product cannot be removed from the stone without destroying the stone’s structural cohesiveness; attempts to remove the lead-glass result in the destruction of the stone (it crumbles or falls apart).
- The lead-glass filler is not colorless. The lead-glass is usually tinted. When analyzed, the lead-glass used has been tinted in order to improve the color seen in the finished product, so one cannot know what the actual color is.
- Weight: Ruby
weight is indeterminable with these products. Lead-glass weighs much more
than ruby, but since the lead-glass cannot be removed, and its high RI
makes it impossible to ascertain exactly how much glass versus ruby is in
a particular stone without expensive, sophisticated instrumentation, it is
not possible to accurately determine the weight of the ruby component. Therefore you cannot calculate the
actual ruby weight, which the FTC guides already mandate. The only thing
certain about the ruby weight is
that it is less than the weight
indicated for the entire stone, and in many cases, much less.
This has been noted by respected laboratories around the world, and is indicated on the AGL reports on lead-glass products. One can only estimate the percentage of ruby versus glass in the stone based on the presence of characteristics found only in glass (bubbles, blue-flash, surface crazing), or only in ruby, but a precise weight cannot be known.
Lead-glass products lack the durability of ruby:
o Lead-glass is much softer than ruby (and other glasses used in treatments) and wears more quickly than ruby.
o Lead-glass is much more vulnerable to scratching, chipping and breaking with normal wear.
o Lead-glass is vulnerable to acid-etching by many substances, including lemon juice.
o Lead-glass composites are quickly and irreparably damaged by techniques that have been routinely used for centuries on ruby or treated ruby; these techniques include the use of heat, chemicals and acids that are routine in making or repairing jewelry containing such products.
o The “joins”—the planes—between the lead-glass and ruby weaken the overall structure of the product, making them more susceptible to damage from an accidental knock or blow.
Lead-glass rubies are being sold to consumers for hundreds to thousands of
dollars per carat, when the cost should be 5-10 times less than what they
are paying. Within the trade, lead-glass rubies under 5 carats each
originally entered the market at prices between $1.00-5.00 per
carat. Today, trade acceptance of these as “just another type of treated
ruby” has resulted in sharply higher prices for the same sizes/qualities,
now costing $10.00-20.00 per carat. Jewelry containing these stones is
being sold by some vendors to the trade at highly inflated prices, which
are then even more highly inflated when sold to consumers.
o Retailers purchasing jewelry pieces containing these stones are told they are rubies and are themselves paying very inflated prices for the pieces they buy, and then passing on their mistake to their customers at even higher prices. While they are easy to distinguish from rubies or treated rubies, most jewelry retailers have not taken the time to learn what the distinguishing characteristics are, and describe and price what they sell based on what they are being told by vendors, who often are doing the same thing with regard to their own sources.
o The unscrupulous are misrepresenting them knowingly, and selling them at huge profits.
It is for the foregoing reasons that I have been – and remain – strongly committed to making the public and trade alike that these are not “genuine rubies” in any way and should not be sold as ruby or “treated ruby.”
The FTC is currently revising its guides for the jewelry trade, and I believe it is essential that the FTC understand how these lead-glass filled ruby products differ from other products in the market that are accurately described as “treated ruby” (or sapphire, or other gemstone name), and how selling them as “ruby” or “treated ruby” violates current FTC guides. I encourage anyone who agrees with me to send a letter to the FTC asking that the guides for the jewelry trade be revised to make it a misleading and deceptive trade practice to sell lead-glass filled rubies and sapphires as genuine ruby, treated or otherwise, as anything other that a composite product or other terminology that makes it clear they are not ruby or sapphire.
It should be noted that you must also be very cautious about buying any blue, green, pink and yellow sapphire since this same type of product is now imitating these other colors of corundum and have different physical characteristics, a much lower value, and the need for special care to avoid breakage or severe and irreparable damage.
Footnote: What Is “RI” and How Does It Affect Quality Grading?
The refractive index of a stone relates to how light moves through, and between, different media—in this case, ruby and glass. The greater the difference between the RI of each substance, the more easily one can see important internal characteristics; the closer the RI, the more difficult it is to see them. If the RI is essentially the same for both substances, one cannot distinguish where one ends and the other begins. This is why other types of glasses sometimes seen in ruby (usually silica glass) are different from these lead-glass products and can be sold as "treated ruby;" they have lower RIs so one can actually see where the fracture is and properly grade the stone.
The RI of lead-glass is almost a perfect match to that of ruby. This means that as light moves through the stone, one cannot see where one substance ends and the other begins. This is why, in lead-glass products, one can’t see the fractures, and thus can’t evaluate the stone’s clarity. It is virtually impossible to determine how deep or wide—how dangerous—any fractures or fissures might be. Even a single fracture can be extremely dangerous and severely affect the clarity rating, depending on where it is located and how far it penetrates into the stone, and thus its longevity and value.
Below one can see how the quantity of lead present affects the RI—the more lead, the higher the RI. It is clear that the percentage of lead present in the glass used on these rubies is very high:
RI's For Various Glasses:
Glass, Fused silica: RI = 1.459
Glass, Pyrex RI = 1.474
Glass, Flint, 29% lead RI = 1.569
Glass, Flint, 55% lead RI = 1.669
Glass, Flint, 71% lead RI = 1.805
The RI of corundum (ruby/sapphire) is 1.76-1.77. From this chart you can see that in order to have the same RI, the lead content in the glass must be in the range of 68-69%. The amount of lead in the glass also accounts for it weighing so much more than ruby, or other glasses used in “treated” material.