A composite diamond is when pieces from separate stones are fused together to create a single diamond. When two diamonds are connected, they are called doublets, and when three pieces are brought together, they are called triplets.
There are several reasons to create a compound diamond. One is for improved appearance or the color of the diamond. Another reason is for better base support and luster of the stone. A third reason to create a compound diamond is to imitate another kind of gemstone. One way to identify a compound diamond is to immerse it in a liquid under magnification and to look for the different parts of the piece.