Yes, it is possible to melt diamonds. However, it is extremely difficult and requires a lot of energy. The process of melting a diamond is called sublimation. In order for sublimation to occur, the diamond must be placed in an environment with no oxygen and a temperature that is at least 1800 degrees Celsius (3272 degrees Fahrenheit). When these conditions are met, the carbon atoms in the diamond begin to vibrate so rapidly that they break apart from each other and turn into gas.