The mineral pyrite, or iron pyrite, is an iron sulfide. This mineral’s metallic luster and pale brass-yellow hue have earned it the nickname fool’s gold because of its resemblance to gold. As sulfur cycles through Earth’s atmosphere, oceans and land, it undergoes chemical changes that are often coupled to changes in other such elements as carbon and oxygen. Although this affects the concentration of free oxygen, sulfur has traditionally been portrayed as a secondary factor in regulating atmospheric oxygen, with most of the free oxygen effect done by carbon. However, new findings that appeared this week in Science suggest that sulfur’s role in the oxygen cycle may have been underestimated.