in residual pyrite or ankerite, it could be also present as poorly crystalline
Fe–oxide–hydroxides from sulphides oxidation, such as ferrihydrite
(Ardau et al., 2014; Blowes et al., 2003; Marescotti et al., 2012), not easily
identifiable by PXRD analyses in complex matrixes; the site with the
lowest Fe is Sa Masa.