Unicorn Poop - Globular Pyrite

Well, how do you like that title! My homeschool students enjoy going to the local rock shop. The proprietor is a delightful gentleman who loves his work and love my students. Recently, I have taken to picking up a few rocks for my husband. I think they look very nice in his office. Iron Pyrite, or Fools Gold, is so beautiful. It usually comes in a cubical form of some sort. However, the rock shop got some from a private collection that was round. They don't know the source. The web isn't yielding much on it either. Doesn't it look like something that would come out of the back end of a unicorn? Thus the name was born. As you see in the picture, the top rock is the normal pyrite form. The bottom two show the round or globular pyrite.