Common Enhancements In Emeralds
Emeralds routinely have their surface breaking fissures treated with colorless oil, wax, resin, or other substance. The effect of this emerald treatment is to improve the apparent clarity of the stone. Today, the term “enhancement” is preferred to the word “treatment” in the industry. The American Gem Trade Association (AGTA) has defined an enhancement as:
Any traditional process other than cutting and polishing that improves the appearance (color/clarity/phenomena), durability, or availability of a gemstone.
Regardless of the terminology used, the practice of fracture filling in emeralds is nearly ubiquitous. Experts estimate that nearly all emeralds are enhanced with oil. This is not usually a problem for consumers when the oil enhancement is explained and disclosed. Emeralds that have no oil enhancement are almost non-existent, as the emerald would need to be void of any surface reaching fissures after being cut and polished.
All but the most exceptional emeralds contain eye-visible surface fractures . Early on, gemstone dealers learned that the appearance of these fractures could be improved by soaking the stones in certain oils, including castor, coconut, corn, linseed, olive, palm, peanut, rapeseed, soy, and tung oils.
Occasionally colored oil is used, which may also improve the apparent color of the stone although the practice is generally frowned upon. It is not considered ethical for green beryl or poor-quality emeralds to be treated with color enhancing oil or resins—whether it is to give them new color, intensify existing color, and/or improve the uniformity of the color—unless, of course, there is full disclosure.
Oil treatments are not necessarily permanent and stable. With time, heat, or improper cleaning, the oil may evaporate, change color, or leach out of the stone. But, this is not a serious problem because emeralds can be re-oiled if the oil is accidentally removed or it has become discolored.
Natural and synthetic resins are often used instead of oil because the beneficial effects last longer. Natural resins such as Canadian balsam as well as manufactured resins and polymers including Opticon, ExCel, and Permasafe, are more durable than oil treatments although they too have been known to dry out, crack, or change color. Once this happens, it is difficult and sometimes impossible to remove all traces of the resin from a stone, especially if a hardener (also called a plasticizer or stabilizer) was added to prolong the longevity of the treatment.
Until recently, fracture filling was a technique applied to cut or finished emeralds only. Now, some have started applying resins to emerald rough before it is cut into a gemstone. This increases the yield from the rough because it allows gems to be fashioned from crystals that would have been considered too fractured and brittle to cut. This means that an emerald gemstone can, in a sense, be “created” by the addition of a kind of “adhesive” or “glue.” When this “glue” or resin breaks down, the emerald will simply fall apart.
Many, many products designed to fill fractures in emeralds have been introduced to the world market. Because fracture filling has grown increasingly prevalent, labs and gemstone dealers felt the need to establish a common standard for identifying and classifying the enhancing agents used in various countries.
In 1999, experts gathered in Switzerland and hammered out an accord or protocol, which is, essentially, a three-tiered system for describing fracture filled emeralds in the trade. Although it is not universally accepted or implemented, the Bern Agreement identifies three levels of disclosure:
- Level 1 identifies the stone as a natural emerald with colorless or colored fillers.
- Level 2 describes the degree of filing as minor, moderate, or significant.
- Level 3 identifies the type of filler upon request if a determination can be made.
A trained gemologist can identify stones that have been filled, although many agree it is extremely difficult to identify the specific type or types of filler in most cases. Fissures or cavities that have been fracture-filled can be readily identified under a microscope. The telltale signs include color flashes, trapped air bubbles, flow structures, and surface “sweating” if heat is applied. Some fillers may also fluoresce under UV lighting.
Although the U.S. Federal Trade Commission indicates that all enhancements should be disclosed, some in the industry feel that it is senseless to disclose fracture filling because the practice is nearly universal. Some experts have suggested instead that only certain difficult-to-remove epoxy fillers be disclosed. Despite the debate, at present, full disclosure is the only ethical practice.
When purchasing emeralds, it is always wise to inquire about their treatment history. Dealers are required to disclose all known treatments. In general, consumers should assume that a stone has been oiled unless the dealer specifically indicates that this is not the case. Non oil-enhanced emeralds sell at an extreme premium prices and need to be accompanied by a certificate from a recognized, independent gemological laboratory.
It may be useful to know that the least expensive emeralds are frequently treated with epoxy fillers because they are durable and effectively mask heavily fractured stones. If your emerald is priced in the thousands of dollars, you should inquire about the extent of fracture filling and whether a colored or tinted product was used. If your emerald is worth tens of thousands of dollars, you should expect the salesperson to be able to tell you the amount of clarity enhancement the stone received and what type of filler was used.
Aside from treatments, or enhancements, emeralds have also been simulated in labs. We explore that process and what you need to know next with Emerald Simulants.