How do you like your rubies — leaded or unleaded?
Lead-glass is the latest additive to bargain-basement rubies. It masks a badly fractured stone, but the result is no match for high-quality ruby.
Rubies with lead-based glass filler began appearing on the market about two decades ago. But in the past few years, the trickle has turned to a flood.
Leaded: Low-quality ruby, is filled with lead-glass to conceal inclusions, can wholesale for $2-$15+ per carat
Unleaded: Ring with a single 4-carat natural Burma ruby even with some inclusions is valued at $50,000
There’s nothing new about gemstone clarity enhancements. Emerald, for example, is commonly fracture-filled to improve its appearance.
For the supplier, fracture-filling is a money-maker. The treatment
- is inexpensive;
- makes a low-quality ruby look better;
- greatly increases the amount of rough gem material that can be used for jewelry, material that previously would have been discarded as too fractured and unattractive.
For the buyer and insurer, this treatment
- increases the potential for fraud, because low-quality material can be passed off and priced — as gem-quality;
- may break down.
Glass filling, requires disclosure!How Bad Is It?
Glass Isn’t Ruby. These stones are often so heavily treated that it is not always possible to determine how much of the stone is actually ruby and how much is glass. In their natural state, these stones are translucent to opaque, with extensive cavities, channels and fractures.
Durability of the Filling. Researchers have found that when a filled stone is heated to high temperature, the filler begins “sweating” and after a few moments flows out of the stone. The filler also becomes damaged when exposed to solutions used for cleaning gems, and is even harmed by common household products such as bleach, ammonia and lemon juice. Once the filling breaks down, the stone’s fractures are again visible.
Weakness of the Gem. Corundum (ruby and sapphire) is one of the hardest materials known (9 on the Mohs scale—only diamond is harder) and its toughness rating is “Excellent.” Yet a highly fractured ruby that’s held together by filler could fall to pieces if the filler is destroyed.
The Mask. Fracture-filling merely masks a low-quality, unattractive and weakened stone. Fracture-filled rubies are worth much less than untreated natural rubies, but the treatment is not always disclosed.
Although the new lead-glass treatment can usually be recognized by a gemologist, many jewelry retailers are not gemologists and do not even examine the gems they sell. A less-than-honest jeweler could leave off mentioning the treatment, while emphasizing the stone’s low price.
AGL now identifies these stones as “composite ruby.” This term immediately distinguishes such a highly adulterated stone from ruby that is not fracture-filled.
Besides listing the heat enhancement, which is standard for rubies, it also specifically lists the lead-glass treatment as an “additional enhancement.” This alerts the buyer/insurer that the stone has been subjected to a treatment that is outside the jewelry industry’s standard.
On our appraisal, the report states,
“This ruby has been heavily treated using a high refractive index lead-glass to fill fractures and cavities, vastly improving the apparent clarity and potentially adding weight. The glass may be damaged by a variety of solvents, heat and ultrasonic cleaning”