Some emeralds contain materials trapped within them during the formation process, as well as some internal or external fissures. These aberrations inside the stone are technically called inclusions but they are often as well referred to as jardin (garden, in French). Inclusions are very common, even being found in the highest quality emeralds, so they are accepted in the jewelry industry. In general, however. the less inclusions an emerald contains, the higher its price.
The most common characteristic that affects the transparency of an emerald are the fissures, which result from the tectonic forces that occurred during the formation of the gemstone. In order to make these inclusions less visible and to improve the gemstone’s beauty and clarity, the emeralds undergo a treatment. This treatment consists on filling the fissures and fractures with a substance, such as oil, resin or wax, to permit a better passage of light, which is blocked by the inclusions.
The treatment is categorized on a scale: none, insignificant, minor, moderate and significant. Minor means the treatment was applied only on the surface of the stone, while significant indicates an evident effect on its aspect.
Hundreds of years ago, the practice of immersing the emeralds in oil to fill the fissures and give them a better look was developed by cutters and quickly it became a common practice in the jeweler’s guild.
The type of treatment is selected according to how much the emerald is included, which is defined through categories used by gemologists:
Regarding the type of substances used in the treatment of emeralds, oil is the most traditional and widely used. Hundreds of years ago, the practice of immersing the emeralds in oil to fill the fissures and give them a better look was developed by cutters and quickly it became a common practice in jewelers’ guilds.
However, other substances, such as synthetic permanent fillers and resins, are also used for the treatment with equal or even better results than oil. It is important to mention that the effect of treatment generally degrades over time, making the inclusions visible again. In this case another treatment will enhance the gemstone one more time.
Almost all emeralds in the world have some type of treatment, with the practice having been down since the beginning of the emerald trade. Furthermore, treatment is another factor that helps to determine the value of a gemstone. It adds to the rigorous and even mystical process around the discovery, cut and enhancement of an emerald, before the gemstone finally reaches the hands of whoever will be fortunate enough to own it.