jarosite

{{Infobox mineral | name = Jarosite | category = Sulfate minerals | boxwidth = 24 | boxbgcolor = | image = Jarosite on quartz Potassium iron sulfate Arabia District, Pershing County, Nevada 2779.jpg | caption = Jarosite on quartz from the Arabia District, Pershing County, Nevada | formula = KFe3(SO4)2(OH)6 | IMAsymbol = Jrs | molweight = 500.8 g/mol | strunz = 7.BC.10 | dana = 30.2.5.1 | system = Trigonal | class = Rhombohedral (m) H-M symbol: (m) | symmetry = Rm | unit cell = a = 7.304 Å, c = 17.268 Å; Z = 3 | color = Amber yellow or dark brown | habit = Crystals are usually pseudocubic or tabular, also as granular crusts, nodules, fibrous masses or concretionary. | twinning = | cleavage = Distinct on {0001} | fracture = Uneven to conchoidal | tenacity = Brittle | mohs = 2.5–3.5 | luster = Subadamantine to vitreous, resinous on fractures | refractive = nω = 1.815 to 1.820; nε = 1.713 to 1.715 | opticalprop = Uniaxial (−), usually anomalously biaxial with very small 2V | birefringence = 0.102 to 0.105 | pleochroism = E colorless, very pale yellow, or pale greenish yellow, O deep golden yellow or reddish brown | streak = light yellow | gravity = 2.9 to 3.3 | density = | melt = | fusibility = | diagnostic = | solubility = Insoluble in water. Soluble in HCl. | diaphaneity = Transparent to translucent | other = Strongly pyroelectric. Non-fluorescent. Barely detectable radioactivity | references = }}

Jarosite is a basic hydrous sulfate of potassium and ferric iron (Fe-III) with a chemical formula of KFe3(SO4)2(OH)6. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides. Jarosite is often produced as a byproduct during the purification and refining of zinc and is also commonly associated with acid mine drainage and acid sulfate soil environments.