Platinum ores sulphides

In this area, the PGM are distributed in (a) disseminated sulphides, mostly in pyrrhotite, chalcopyrite and pentlandite. The predominant platinum minerals are Pt-Fe alloys, cooperate (PtS) and sperrilite (PtAs2) (b) massive sulphide ores where the predominant PGM are Pt-Fe alloys, rustenburgite (Pt3Sn) and sperrilite (PtAs2), occurring in fine inclusions in chalcopyrite and pyrrhotite and finally (c) disseminated veins and brecia ores that may consist of mainly chalcopyrite or pyrrhotite. The PGM in these ores is present as Pt-(cooperate) and Pd-(rysotkite) sulphides. 

The ores from this region are of tholeiitic intrusions hosting Cu-Ni sulphides with relatively low PGM content. In these ores, most of the palladium is associated with pentlandite, where the platinum and rhodium are mainly associated with pyrrhotite. Only sperrilite and Pt-Fe alloys have, so far, been found in these ores. 

Electrolysis of the resulting solution in a diaphragm cell with carbon or platinum cathodes resulted in liberation of arsenic in the cathode compartment. Extraction of the ores with sulphydroxides of the alkaline earth metals and subsequent electrolysis has also been suggested.4 These methods have little application, however, since the arsenic in the common ores, such as arsenopyrite and ieucopyrite, cannot be extracted as sulphide. 

Figure 4.27 Chondrite-normalized platinum group element plot. The data are for komamte-massive sulphide ores from Alexo Mine, northen Ontario (from Barnes and Naldrett, 1986). The chondrite -normalizing values are given in Tabic 4.11, column 2 and are taken from Naldrett and Duke (1980).

PolyMet Mining Corp. (PolyMet) is advancing the development of the NorthMet Project. The NorthMet deposit is located in northern Minnesota, adjacent to the historic Iron Range. The deposit was discovered in the 1960 s and consists of a large, magmatic, disseminated sulphide, polymetallic deposit with values in Cu, Ni, Co, Zn, Au, Ag and Platinum Group Metals (PGM). The shallow, tabular orebody may be mined by open-pit methods with minimal pre-strip and a low waste ore strip ratio. 

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