Aquamarine, the modern March birthstone as adopted by the American National Association of Jewelers in 1912, is a variety of Beryl that is transparent and of various shades of blue and blue-green; almost all the specimens of the preferable sky-blue in color are (since 1920) the result of heat treatment applied to greenish or yellow-brown beryls. The stones are dichroic, and are usually cut as a brilliant or step cut. They resemble the Emerald (the chemical composition is identical, as is the hexagonal crystal form) but the stones are paler and, being less rare, are much less valuable. They also resemble euclase and blue Topaz, from all of which (as well as from glass imitations and synthetic gemstones) they can readily be distinguished. Aquamarines on the market today are usually faceted, but when cut as a cabochon, they may display a cat’s eye effect known as asterism.
There are many sources, but Brazil has produced the finest and some very large specimens, e.g. one found in 1919 weighing 243 Lb. Some ancient aquamarines were engraved with portraits, e.g. one with a portrait of Julia, daughter of the Roman Emperor Titus. The synthetic stone resembling aquamarine is the blue Synthetic Spinel.
Folklore, Legend, and Healing Properties:
Since early times, aquamarine has been believed to endow the wearer with foresight, courage, and happiness. It is said to increase intelligence and make one youthful. As a healing stone, it is said to be effective as a treatment for anxiety and in the Middle Ages it was thought that aquamarine would reduce the effect of poisons.
A legend says that sailors wore aquamarine gemstones to keep them safe and prevent seasickness.