Identification Tools Required: Magnification, Chelsea filter, diffraction grating spectroscope.
How to Identify:
Primary Test: Magnification. Just as the flux melt synthetic method imparts diagnostic internal features, so does the hydrothermal. The growth pattern that is seen so often in other hydrothermal gemstones is also to be found in the hydrothermal emerald. As you view the images below you will see the long cellular structure of the hydrothermal emerald that is the primary test to identify this synthetic emerald.
Secondary Tests: The Chelsea filter will be a very important tool due to the fact that synthetic hydrothermal emeralds will contain far more chromium used in the synthesis to give the stones the best possible green color. As a result of this the red reaction of the Chelsea filter will usually be very intense with the synthetic emeralds, far more than naturals.
Another result of the higher amount of chromium in the hydrothermal emerald is that the chromium lines in the spectroscope will be more intense and clear than is normally seen in naturals. The greater concentration of chromium in the hydrothermal emeralds will provide a text book reaction in the spectroscope. For those experienced with observing natural chromium based emeralds through a spectroscope the difference in the intensity of the Cr line can be a very strong indicator for a all synthetic emeralds.
Additional inclusions that will be found in hydrothermals include breadcrumb type inclusions with nail head spikes. While rare to find without high magnification, the breadcrumb inclusions are a strong indicator of a hydrothermal gemstone.
Rarely found will be emeralds showing the hydrothermal seed plate. All hydrothermal emerald crystals grow by the use of a starter seed plate on which the synthetic emerald material grows as it cools. Due to the current market conditions some producers are using the crystal all the way into the seed plate in order to maximize the return from the process. The result is an emerald that displays the seed starter plate within the stone. While rare, it can be confusing to the inexperienced as the seed plate and resulting inclusions can appear as natural internal features. Great care should be given when evaluating highly included emeralds as shown below.
One additional indicator that will rarely be found in hydrothermal emeralds is gold crystals as seen below. The Russian labs once used gold lined autoclaves to grow the hydrothermal emeralds and occasionally we have found gold crystals in the emeralds. These gold crystals are due to some of the gold from the wall of the crucible coming off and melting in the mix. As the crystal formed the gold reformed inside the emerald as gold crystals. While this is rare, it is also diagnostic for a synthetic emerald.
Repair and Setting: As a true synthetic emerald normal care should be taken as with natural emerald. No heat on or near the stone. The one good issue is that these lab grown emeralds are not oiled or treated for color enhancement using processes that can be removed by ultrasonic cleaning. Care should still be taken when cleaning not to over heat the stone. However since the stones are not oiled this removes the concern of special care regarding that issue.