Emeralds are not diamonds. The emerald is a coloured gemstone, made from a green hued mineral called beryl. In contrast, diamonds are made from carbon, can be coloured or colourless, and are the hardest known gemstone.
You have heard of the emerald cut. A gorgeous rectangular shape with bevelled corners, this striking shape is used for many gemstones (including diamonds) to inspire a vintage aesthetic. While the emerald itself is green (or sometimes red), the emerald cut suits almost any jewellery, such as, emerald diamond necklaces, bracelets, rings and more.