Fig. 4. Microphotography by scanning electron microscopy (SEM) of soils in the interior of the reddish-yellow layer (at 2 mm from the contact point with the tailings). Photo 4.1: (SEM–energy dispersive spectrometry [EDS]) tabular crystals of gypsum (G) in a mass of Fe oxyhydroxides (O). Photo 4.2: (SEM–EDS) acicular crystals of Al sulfate (A) in a mass of sulfates of Fe, Al, Zn, and Ca (S).