Zircon resembles diamond in luster and fire and colorless zircons have been mistaken for diamonds by experienced jewelers. It is found in browns and greens but can be heat treated to beautiful blue and golden colors. Zircon has been used as a diamond simulant both for innocent and nefarious reasons. Zircon can make a very attractive and affordable gemstone. Colorless material is produced in this way as well. Zircon is the December Birthstone.