Pyrite is widely known in the coal industry as a major source of sulfur in coal. Something that is not desired. Prior to concerns over sulfur dioxide emission, Pyrite was knows as "Fools Gold". Pyrite is a Iron Sulfide, and has a shiny, yellow to brass appearance. Gold is commonly found in sulfide deposits, so many a prospector took home samples of Pyrite, (and some still do this, even today) thinking they had struck the motherlode, only to find the assay was zero parts gold. Pyrite has been processed to recover the sulfur, mainly in the form of sulfuric acid, but it is a relatively minor ore for commercial sulfur production.