Emerald is the green to greenish blue variety of beryl, a mineral species that also includes aquamarine as well as beryls in other colors. Gem experts differ on the degree of green that makes one stone an emerald and another stone a less-expensive green beryl. Some people in the trade tend to give the name emerald to any green beryl colored by chromium. But to most gemologists, gemological laboratories, and colored stone dealers, it is more correct to call a stone green beryl when its color is “too light” for it to be classified as emerald. Even among that group, however, there’s a difference of opinion about what’s considered “too light.”

For over 5000 years, emeralds have been one of the most desirable and valuable colored stones Ancient civilizations in Africa, Asia and South American dependently discovered emeralds and made them a gemstone of highest esteem. In the United States and many other countries, emerald serves as the birthstone for people who were born in the month of May.

Today emerald, together with ruby and sapphire, form the “big three” of colored stones. The “big three” generate more economic activity than all other colored stones combined. In 2015 the value of emeralds imported into the United States exceeded the value of all colored stones outside of the “big three” combined.