Seasonal variations in the formation of Al and Si rich Fe-stromatolites in the highly polluted acid mine drainage of Agua Agria Creek (Tharsis, SW Spain)

► Jarosite and rostite were observed as Fe-stromatolites forming minerals. ► Al and Si enrichment in the Fe-stromatolites reflects the extreme water chemistry. ► Seasonal variations in water chemistry was linked to the precipitates mineralogy. ► Diatoms distribution in the Fe-stromatolites reflects water seasonal variations. ► A detailed description of an extreme environment resembling Mars surface was offered.