Pyrite is an iron sulfide with a very metallic luster that looks a lot like real gold. Back during the gold rush in the mid 1800's, many people were fooled by Pyrite, thus its other name "Fools Gold."
I love pyrite. My favorite are the specimens that form naturally into cubes. (see the second photograph) How does this occur naturally? Well, iron and sulfur molecules join together and create the most spectacular natural cubic crystal formation. They are just amazing and you won't believe that Mother Nature created them.