Aquamarine is the blue, or perhaps more correctly, blue-green or aqua variety of the mineral beryl. Other gemstone color varieties that belong to beryl include emerald, morganite, and heliodor. Other colors of beryl are simply referred to by their color, such as red beryl.

Aquamarine is colored by trace amounts of iron that find their way into the crystal structure. Most gem aquamarines have been heat treated to produce the popular blue-green colors from less desirable yellow or pale stones. The leading producer of aquamarines is the country of Brazil, which has many mines. Pakistan, as well as many U.S. localities, produce wonderful specimens as well.