REVIEW OF PLATINUM-GROUP MINERALOGY: COMPOSITIONS AND ELEMENTAL ASSOCIATIONS OF THE PG-MINERALS AND UNIDENTIFIED PGE-PHASES

Abstract

There are 96 approved PG (platinum group) - mineral species and more than 500 unidentified PG-phases on record. In addition, over 20 non-PG-minerals contain varying concentrations of one or more of the six platinum group elements. The PG-minerals commonly have cubic symmetry and density Values mostly between 10-11 g/cm(3) but within the range 5-22 g/cm(3). Furthermore, there is a tangible positive correlation between relative density and reflectance data. On a chemical basis, all PG-minerals and PG-phases are non-silicates and a large proportion are sulphides, arsenides and tellurides. The elements Sb and Bi are also important constituents of PG-minerals. This review of the published literature up to April, 1996, provides an evaluation of approximately 1500 published chemical analyses of PG-minerals which have been accepted by the IMA as discrete mineral species and unidentified PG-phases reported in the literature but not proven to be discrete minerals. Revealed by the database are a number of chemically-related trends which concern both the PG-elements themselves and the essential non-PG-element constituents. The latter grouping of elements is discussed as a separate publication (Daltry and Wilson, 1997). Pd-dominant compounds are the most abundant of the PG-minerals and PG-phases and the Os-dominant compounds are the least abundant. On an inter-PG-element basis, the Ir-, Os-, Pd-, Pt-, Rh-and Ru-dominant minerals and phases may each contain varying concentrations of all the remaining five PG-elements. In this context, there are discernable sympathetic and antipathetic trends. Palladium exhibits the most pronounced antipathy with other PG-elements, whereas platinum exhibits the most marked sympathetic tendencies towards the other PG-elements.