Jarosite [KFe₃(SO₄)₂(OH)₆] occurs commonly in the oxidised portions of sulphide ore deposits, fluvial environments contaminated by acid rock or acid mine drainage (ARD, AMD), wastes produced from the metallurgical extractive industry, acid sulphate soils and clay seams and beds, and readily breaks down when removed from its stability region by presumably converting to iron(III) oxide or oxyhydroxide phases. When subjected to reducing conditions, these conditions can trigger the Fe²⁺-induced transformation of jarosite to more stable Fe(III) minerals, such as goethite with a rise in pH . There are many reduced organic matters in the wild which are able to reduce Fe(III) (oxyhydr)oxides to aqueous Fe(II). Because of the influence of organic matter，original reactant or the final product，in the system，the secondary Fe phases of Fe²⁺-induced transformation of jarosite may be difference comparing to adding aqueous Fe(II) directly. Also previous studies of the interaction of reduced organic matters with iron oxide have largely focused on the reactivity of the iron oxide, with kinetic equations used to describe the reductive dissolution process, there is little focuse on the transformation of minerals. Here we investigate the transformation of jarosite in the presence of cysteine to examine the impact of the naturally occurring reducing agent on such an Fe(II)-catalyzed transformation of jarosite. The transformation of jarosite to possible secondary Fe(III) mineralization products was identified using XRD, SEM, FTIR and TEM. Previous studies showed that the Fe(II) adding directly has resulted in transformation of jarosite to lepidocrocite and goethite via an intermediate green rust (GR-SO4) phase , but only lepidocrocite was found in this study. Further experiments indicated that this was possible due to the presence of cysteine disturbed the rate and amount of Fe(II) transport to the oxide surface, including formation of Ferrous-Cysteinate complexes and adsorption of cysteine，inhibiting the formation of goethite. These results have implications for further study of environmental mobility and bioavailability of incorporated metal(loid)s.

^*This study was supported by the National Natural Science Foundation of China (Nos. 41330639, 41720104004)