Fools' gold

By means of fools' gold, copper coins can temporarily be changed to gold pieces, or brass items turned to solid gold, although creatures examining the items closely might discern their true nature. If the "gold" is struck hard by an object of cold-wrought iron, there is a slight chance it will revert to its natural state.

Note: This version of fools' gold originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.