Occurrence of some Ni- and Sn-rich minerals in copper converter slags

ABSTRACT. The chemistry of opaque spinel, delafossite (Cu20 9 Fe203) , cuprite (Cu20), cassiterite, nickel-olivine (Ni2SiO4), and bunsenite (NiO) from some copper con-verter slags has been investigated by electron microprobe analysis. The spinel has a complex composition contain-ing up to 33.89 ~ NiO and 47.69 ~ SnO2, ranging from essentially Ni2SnO 4 to (Ni,Fe2+)Fe23+O4. The asso-dated elafossite contains up to 19.18 ~ NiO and 38.15 SnO2. The chemical variation of the mineral phases is evaluated, and it appears that Ni 2 § enters the spinel and delafossite to charge-balance the octahedrally co-ordinated Sn 4+. THIS paper describes the mineralogy of some slowly cooled copper converter slags, which had been cast into approximately hemispherical l dles 1 m in diameter and allowed to air-cool. From the large number of samples collected, three main mineral assemblages have been recognized: 1. nickel-olivine (Ni2SiO4)+spinel+delafossite (Cu20- Fe203) + cuprite (Cu20) + cassiterite + bunsenite (NiO) 2. cassiterite + spinel + delafossite + cuprite 3. spinel + delafossite + cuprite. All samples contain yellow to orange-yellow coloured glass, which represents rapidly cooled residual liquid, and shows no evidence of devitrifi-cation. Fifteen specimens, chosen as representative samples, have been studied to investigate the petrography and crystal chemistry of these con-verter slags, which have essentially SnO2-NiO-ZnO-Cu20-PbO-Fe-oxide-SiO 2 bulk composi-tions. Analytical techniques. The compositions of the phases were determined by extensive electron microprobe analysis using a C.S.I. Microscan 9 instrument. Computer corrections for ZAF effects were applied to all raw data. Spectrometer scans were used to detect the constituent elements for each phase. Electron microprobe analysis is occa-sionally complicated by interferences betwee