Emerald cut diamonds have been around for centuries. An emerald cut diamond is a redtangular shape, step cut diamond. Never confuse emerald cut with an emerald, which is a green gem that is part of the beryl family. Some people confuse emerald cut diamonds and princess cut diamonds. Princess cuts are generally square, but can be rectangular shape as well. From the sides princess cuts are an inverted pyramids. Many people love the classic, vintage look of an emerald cut center diamond.