Emerald is well-known as the birthstone for May. Emerald is a variety of the mineral beryl, colored green by trace amounts of chromium. In the United States, emeralds colored by vanadium are recognized as true emeralds, but in Europe, vanadium emeralds (sometimes called "Columbian Emeralds") are simply called "green beryl". Our beads are generally cut in China, and sometimes India. They are more likely to be chromium emeralds, but we are unable to confirm this. Most emeralds -- even in the fine jewelry industry -- are oiled as part of the post-cutting process. This improves clarity and stability. Bead-quality emeralds are almost guaranteed to be oiled, with either a natural or synthetic oil with refractive index close to that of an emerald. With bead-quality emeralds, the oil may have added color, although this is not acceptable with higher-grade emeralds. When cleaning emeralds of any quality, clean only with a soft cloth. Avoid tumblers, ultrasonic cleaners, and harsh chemicals.