Sub Category: Fairy money turned to Dross

Title: Alternative Version of the Cruel Man and a Fairy Dog

A person discovered a lost Fairy dog wandering about, and took it home, but he did not nurse the half-starved animal, nor did he nourish it.  After a while some of the Fairy folk called on this person to inquire after their lost dog and he gave it to them.  They rewarded this man for his kindness with a pot filled with money and then departed.  On further inspection, the money was found to be cockle shells.