The changes in surface properties and the leaching of chalcopyrite CuF
eS2 after ultrafine grinding are examined. Surface area measurement an
d photoelectron spectroscopy (XPS) were used for characterization of t
he ground samples. A gradual decrease in the particle size, from 32 mu
m, for as received CuFeS2, to 2 mu m, for the sample ground for 60 mi
n, as well as increasing the surface area from 0.23 m(2) g(-1) to 2.68
m(2) g(-1) for equal samples was observed. Analysis of the XPS line o
f sulphur S2p electrons has shown the existence of sulphur in three di
fferent chemical forms: S2-, S-0 and S6+. The ground samples exhibited
a greater proportion of higher oxidation states. The samples were che
mically preleached with an acid solution of Fe(III) sulphate to an equ
al conversion degree (epsilon(Cu) = 25%), characterized and subsequent
ly leached by the bacteria Thiobacillus thiooxidans. While the rate of
chemical leaching is proportional to the increase in CuFeS2 surface a
rea, the rate of subsequent bacterial leaching is limited by 15 min gr
inding. The different behaviour of the samples ground for a long time
may be explained by differences in the chemical composition of surface
layers.