Compounds with mixed and intermediate sulfur valences form cloudy small inclusions in banded pyrite and 2–4 mm large rounded aggregates in pyrite stalactites. Such areas under high magnification of SEM appear to be a mixture of FeS₂ with FeS₂O₃. Some of the microareas of 40–50 m are homogeneous and can be identified by reflected light microscopy, microprobe and soft X-ray spectroscopy as Fe-thiosulphate, FeS₂O₃ or (Fe, Pb)₂S₃O₇ with this compound having one sulfur –2 and two sulfurs +6. The intermediate sulfur compounds are enriched in Pb, Ni, Co and As.