The evidence is one or more of the following:
a. The presence of jarosite (KFe3(SO4)2(OH)6);
b. Directly overlying sulfidic materials; and
c. 0.05% water-soluble sulfate.
Jarosite is a straw-yellow mineral formed as a result of pyrite oxidation (Dent, 1986; Minh et al., 1997; Shamshuddin and Auxtero, 1991;Shamshuddin et al., 1995; van Breemen, 1976). Once it is formed, it will remain in the soils for a long time before it is finally weathered to form
oxides of Fe, such as hematite, which is reddish in color.