Lead-Glass Filled Ruby:  A Case Study in Misrepresentation and Deception

By Antoinette Matlins, PG

I find it very disturbing that there are still many people in the gem and jewelry field who still do not 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 are even objecting to what the laboratories are calling them!

I felt so strongly about the unprecedented issues these lead-glass imitations presented that I added extensive information about them in the latest edition of Jewelry & Gems: The Buying Guide (7th Edition) and an entire new chapter to the fifth edition of my book Gem Identification Made Easy (which just rolled off press a month ago). But since this has become a social media era, let me attempt here to clarify the differences, and why selling lead-glass products as genuine “treated rubies” (and now “treated sapphires” as well, which we are finding in beautiful shades of blue, yellow, and pink) is misleading and deceptive.

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 recent years, we’ve also seen more extreme levels of heating that require borax coatings (which can melt from the heat and leave residue in fissures), and glass fillings used in fractures to reduce their visibility. A few years ago, however, we began seeing a new ruby product at gem shows, offered for a few dollars per carat. Most of these “rubies” 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” any ruby while doing routine jewelry work suffered damage to their reputations, loss of customers, and were held financially responsible by retailers and/or consumers. This was unheard of … until the lead-glass “rubies” entered the market. So gemologists had to ask, what’s different about these? Why don’t they respond as ruby should respond? So gemologists from the Accredited Gemologists Association (AGA), myself among them, purchased stones from various vendors at various shows and conducted 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 highly refractive lead-glass in particular—combined with some unknown 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); they were, in fact, a blend of two materials that are altogether different in terms of physical properties.

It became clear very quickly why the producers were using lead-glass: lead-glass is essential because it makes it impossible to see where the corundum ends and the glass begins! The high refractive index (RI) obtained by introducing lead into the glass is virtually identical to that of corundum, which means it is impossible to distinguish one from the other. Furthermore, the refractive index—one of the most important tests used to identify any gemstone—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 (the instrument used to determine a stone’s RI) so that it is actually testing the glass, the RI will be indicative of ruby or sapphire! (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 became an integral part of the blended product and cannot be removed without destroying the entire “gem.” This is critical for several reasons, but one important difference this makes is that the properties associated with “ruby” are no longer the same since the properties of lead-glass are so different. In addition, the lead-glass component represents a much more significant percentage of the stone than what is found in “treated rubies” which contain some miniscule amount of silica glass (the type of glass used in certain types of treated ruby, and which can be removed without any damage to the stone) … and these two very different materials are inseparable.

There are two critical differences between “treated ruby” and the lead-glass product: 1) It is impossible to see where the glass actually is so you cannot determine how much of the stone is glass versus how much is 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 fusion of these two very different materials creates something that is neither ruby nor glass, but a new type of imitation that combines two materials—and the properties of both—each of which is 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—are 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 guidelines: 

It is for the foregoing reasons that I have been—and remain—strongly committed to making the public and trade alike aware that these are not “genuine rubies” in any way and should not be sold as ruby or even “treated ruby.”

Now that the FTC is revising its guidelines for the jewelry trade, 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 guidelines.

It should be noted that we are also now seeing blue, green, pink, and yellow sapphires that are the same type of product, with the same issues for public and trade alike. These are also being treated with a high-RI glass, resulting in different physical characteristics, a much lower value, and the need for special care to avoid breakage or severe and irreparable damage. 

NOTE: 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 glass sometimes seen in ruby (usually silica glass) are accepted; 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 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.