This mistake takes place in the scene where Flint Marko transforms into the Sandman as a result of falling into a sand filled pit that is being experimented upon after entering a prohibited testing facility while being pursued by the police.

In the scene Marko's molecular structure is changed into sand particles by the experiment, even his clothing. With the exception of the locket given to him by his daughter. It could be argued that because it is made of metal it was unaffected by the incident. However Marko wears a belt with a metal buckle that was affected and changes to sand with the rest of him.