Pyrite (FeS₂), often called “fool’s gold,” is mined both as a minor iron source and, more importantly, as a sulfur source for sulfuric acid production. Historically, pyrite roasting was a dominant sulfur source, though modern industries now rely largely on elemental sulfur from oil and gas desulfurization. Still, pyrite remains relevant in regions with mineral-based sulfuric acid production, as well as in specialty metal recovery (gold often occurs with pyrite).