Jarosite is a potassium iron sulfate mineral of composition KFe3(SO4)2(OH)6 usually derived from the oxidation of pyrite and other Fe-bearing sulfides. Sulfide oxidation produces sulfate plus hydronium ions during the hydrolysis of water. Jarosite typically occurs as a yellowish mass, usually in combination with other sulfates, notably alunite [KAl3(SO4)2(OH)6] and natrojarosite [NaFe3(SO4)2(OH)6]