Diamonds may be a girl's best friend, but an emerald is a close second. The brilliant green gemstone is often used to craft jewelry pieces, such as an emerald ring or necklace, and is a fabulous choice for a gift. Because emeralds are brilliant green, jewelers like to use them to shape leaves. They are also often cut in a square or rectangle shape. In fact, this is so common that a square-cut diamond or other gemstone is called an emerald cut. You can find many emeralds set with other gemstones for contrast, such as smaller diamonds used to frame a larger green stone. Emeralds use the same four Cs to grade the stones: cut, clarity, color, and carat weight. The darker the emerald, the more valuable it is. If an emerald's shade is too light, it is called green beryl instead of an emerald. There are many reliable sellers on eBay selling a number of different pieces, and even unset emeralds that you can take to a local jeweler to create a custom piece.