Ruby: Red Alert for Bench Jewelers!

Composite rubies behave differently from treated rubies, and knowing the difference can prevent frustration at the bench and safeguard your reputation.

Last edited: 10/30/2019
American Mined Rodeo Queen Rubies

Working on rubies isn't what it used to be because the rubies themselves aren't what they used to be: More and more rubies that are reaching the bench look like ruby, but they sure don't act like ruby!

Have you come across a ruby that broke at the corner while you tried to set it, even though you didn't exert undue pressure? Or had one crumble into a molten glob when using the torch, or become deeply and irreparably acid-etched from the pickle — across the entire stone, top and bottom? This isn't the typical experience one has when working with rubies. So why is this happening now?

What's happening is that most of the low-quality, inexpensive rubies now being sold in the market are not just "treated rubies" but something altogether different—a mixture of low-quality corundum infused with lead glass. The amount of lead glass present in the stones now in the marketplace often exceeds 25% and, in many cases, represents 40% or more of the entire stone! These are being called "composites" by an increasing number of laboratories, and the Accredited Gemologists Association (AGA) has taken the position, based on FTC guidelines and other sources, that these are actually "imitation" products because of the huge percentage of glas and thus cannot be sold as genuine rubies. How can a stone be sold as a ruby if it doesn't "act" like a ruby, have the longevity of a ruby, or have the value of a ruby? (While some sell for $50 per carat or more, most sell for under $10 per carat in any size and shape, and much less when purchased in quantity.)

These composites should not be confused with "treated" ruby, in which glass fillings have been used to reduce the visibility of internal fractures, or with stones treated with traditional techniques involving unusually high heat that can result in minute residues of glass in surface-reaching fissures. These rubies have been around for many years, and the amount of glass is far less than what is found in new composites.

Another important difference is that the glass used in these traditionally-treated rubies is not a lead glass, so one can quickly and easily judge the overall clarity and whether the stone has any durability issues.

imitation ruby
Photo courtesy of Craig Lynch, G.G., Accredited Gemologists Association. "Ruby" was dabbed with fresh lemon juice 4 times in 48 hours.

This is not the case with composites; with the use of lead glass it is very difficult to determine where the glass ends and the ruby begins, so it is easy to miss fractures, the planes between the glass and corundum, or how much is glass is present versus ruby.

If bench jewelers are unable to distinguish the difference between a treated ruby and one of these composite rubies, the outcome can be devastating. If the torch is kept on them, or they are left in the jeweler's pickle just a tad too long, irreparable damage can result—not just to the stone, but to the jeweler's reputation. In addition, the jeweler will probably be held responsible for replacing the stone with something far more costly than the original stone.

Develop an eye for distinguishing characteristics of these composite stones, and inform your customers about the true nature of their stones before beginning work on them.

Anyone interested in knowing more about these stones, please contact me at I'll be glad to send you an in-depth piece I've written on all of the ways in which these are different from anything else in the market. Also, go to the AGA website for more information and excellent images.