Abstract: Jarosite is a very common secondary mineral in acid mine drainage (AMD). It can absorb effectively heavy metallic elements
such as Pb, Zn, Gd, As in AMD. The jarosite formed under different conditions is of diverse microtopography and different adsorption
capacities to heavy metallic ions. In this paper, jarosite was synthesized by chemical and microbiological methods, respectively, and
the samples of sediments with jarosite-bearing secondary minerals were collected form the AMD of Dabaoshan Mine in the north
Guangdong Province. The jarosite formed under different conditions was identified by using SEM and XRD, its microtopographic
characteristics were observed, and the synthesis conditions of jarosite were investigated. The results show that the range of pH values in
which jarosite can be chemically synthesized is approximately 2.0-2.5 at room temperatures. The crystal size of the synthetic jarosite is
about 2-10 μm and the crystalline form is plate-like. Jarosite can also be chemically synthesized at 65℃ with a wider range of pH
values between 2.0-3.0, but the crystalline form is relatively poor. Jarosite can be synthesized by microbial method in a relatively large
range of pH values between 2.0-5.0, which has nearly perfect rhombohedron-shape crystalline form and relatively uniform sizes about
2-4 μm. Jarosite discovered in sediments of AMD occurs in a pH value ranging from 2.5 to 3.5. It is of relatively perfect rhombohedron-shape crystal and the single crystal size is mostly in 1-2 μm. According to the formation conditions and microtopographic
characteristics, the jarosite formed in AMD is probably of microbial origin.

Key words: jarosite, microtopography, chemical method, microbial method, synthesis conditions