An imitation emerald is any colored stone material that looks like a natural emerald and is used for that purpose. A synthetic emerald is lab grown and has the same chemical composition, crystal structure and components as the natural stone.
Colored glass is most often used as imitation emerald. The signs to look for that show they might be glass are “gas bubbles, concave surfaces and rounded junctions”, as described by the Gemological Institute of America.
Other imitation stones would be synthetic spinel, green synthetic cubic zirconia
, green garnet and triplets that consist of two pieces of colorless beryl glued together with, believe it or not, green cement.
Green spinel is most commonly used as imitation emeralds. They are often used as May birthstones as emerald is the birthstone for May.
In 1938, the first marketable synthetic emeralds were produced. High school student, Carroll Chatham, experimented with crystal growth and began marketing them three years later. Russian companies also grew synthetic emeralds as did Chatham Created Gems, Kyocera International.
Each company uses different methods to grow these synthetic emeralds
and each synthetic stone grows in different time periods. In 1953, Carroll Chatham donated a 1,104 carat synthetic emerald to the Smithsonian Institute that took two years to grow.
Although synthetic emeralds and natural emeralds look the same to the naked eye, a gemologist using a microscope can see the difference.
Depending on the method used to grow the emerald, the ingredients used by manufacturers control the color of the stones to match those of natural emeralds. They can also control tone and saturation of the stone.