Determination of minerals in platinum concentrates from the Transvaal by X-ray methods

Bannister, F. A.; Hey, M. H.

doi:10.1180/minmag.1932.023.138.05

Cited by 45 publications

(26 citation statements)

References 6 publications

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“…Solid lines represent the limits of the stability fields of cooperite and braggite at 700°C Merkle 2000, 2002). Data from: Bannister and Hey (1932), Genkin and Zvyagintsev (1962), Laputina and Genkin (1975), Brynard et al (1976), Schwellnus et al (1976), Cabri et al (1978Cabri et al ( , 1996, Toma and Murphy (1978), Watkinson and Dunning (1979), Kingston and El-Dosuky (1982), Mostert et al (1982), Todd et al (1982), Vuorelainen et al (1982), Talkington and Watkinson (1984), Criddle and Stanley (1985), Genkin and Evstigneeva (1986), Volborth et al (1986), Tarkian (1987), Halkoaho (1989), Johan et al (1989), Corrivaux and Laflamme (1990), Cowden et al (1990), Shcheka et al (1991), Auge´and Legendre (1992), Legendre and Auge´(1992), Barkov and Lednev (1993), Coghill and Wilson (1993), Weiser and Schmidt-Thome( 1993), Auge´and Maurizot (1995), Barkov et al (1995), Rudashevsky et al (1995), Cabri and Laflamme (1997), Tolstykh and Krivenko (1997), Auge´et al (1998), Mitrofanov et al (1998), Distler et al (1999, Gornostayev et al (1999), …”

Section: Observationsmentioning

confidence: 99%

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

Merkle

Verryn

2003

Miner Deposita

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Analyses of the Pt-Pd±Ni sulphides cooperite, braggite, and vysotskite reported from worldwide occurrences seem to imply a continuum of compositions between vysotskite and cooperite, with no obvious miscibility gap. This is contrary to the experimentally confirmed miscibility gap between cooperite and braggite, and the established compositional gap between co-existing cooperite and braggite from the Merensky Reef. Although the only unambiguous way of distinguishing between cooperite and braggite is to obtain structural information through X-ray diffraction or equivalent techniques, most identification of Pt-Pd±Ni sulphides is based on microanalytical techniques due to the small grain size of most platinum-group minerals. Ni contents also have to be considered because a classification based on the Pt/Pd ratio alone can be very misleading. Naming of Pt-Pd±Ni sulphide compositions with high Pt contents based on qualitative or semiquantitative analyses should be avoided. Natural PtPd±Ni sulphides which project into the compositional gap (established by experimental work) cannot be named without supporting structural information. Compositions of grains, which plot inside the gap, are considered to be metastable and to result from the loss of Pd through interaction with hydrothermal fluids.Keywords Braggite AE Cooperite AE Pt-Pd-Ni-S AE Miscibility gap AE Bushveld AE South Africa Recent experimental investigations of the system PtS- PdS-NiS (Verryn and Merkle 2000, 2002) confirmed the presence of a miscibility gap between cooperite and braggite and a continuous solid solution series between braggite and vysotskite. Contrary to the experimentally confirmed miscibility gap between cooperite and braggite, a compilation of analyses reported in the literature from worldwide occurrences seems to imply a continuum of compositions between vysotskite and cooperite with no obvious gap (Fig. 1). This contribution focuses on the reasons for the discrepancy between experiments and natural occurrences. The question also arises of which criteria to use for identification of minerals inside the experimentally established miscibility gap. The data baseA compilation of published analyses from the literature (for sources see caption of Fig. 1) was used to evaluate the miscibility gap between cooperite and braggite and the problem of identifying some natural Pt-Pd-Ni sulphides. The database of 592 microprobe analyses from Miner Deposita (2003) 38: 381-388

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Section: Observationsmentioning

confidence: 99%

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

Merkle

Verryn

2003

Miner Deposita

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“…Cooperite belongs to space group P42/mmc and braggite to P42/m (Bannister and Hey, 1932). This miscibility gap between coexisting braggite and cooperite (Fig.…”

Section: Compositions Of Coexisting Braggite and Eooperite (Merensky mentioning

confidence: 99%

Compositional variation of cooperite, braggite, and vysotskite from the Bushveld Complex

Verryn

Merkle

1994

Mineral. mag.

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The compositions of coexisting and individual cooperite (ideally PtS) and braggite (ideally (Pt,Pd)S) grains from the Merensky Reef of the Bushveld Complex, as well as cooperite, braggite and vysotskite (ideally PdS) grains from the UG-2 of the Bushveld Complex were investigated. There is a clearly defined miscibility gap between cooperite and braggite, but no evident gap between braggite and vysotskite. Partition coefficients between cooperite and braggite are determined on coexisting phases. The gbD raggite/c~176 in atomic ratios are estimated to be 0.54 for Pt, 15.81 for Pd and 5.93 for Ni. For Rh and Co the/~D ~ are estimated to be > 1.40 and > 1.46 respectively. No systematic behaviour is detected for Fe and Cu. Coupled substitutions of Pd + Ni for Pt in cooperite and braggite/vysotskite are indicated. Within the cooperite of the Merensky Reef, the Pd:Ni ratio is approximately 9:11. The substitution trend in braggite, which extends to vysotskite in the UG-2, is dependent on the base-metal sulphide (BMS) association. If pentlandite is the dominant Ni-bearing BMS, the Pd:Ni ratio is about 7:3 in the Merensky Reef and in the UG-2. Millerite as the dominant Ni-bearing BMS in the UG-2 changes this ratio to 3:1. It is concluded that the Ni-content in braggite/vysotskite from BMS assemblages does not depend on the NiS activity, but rather on temperature of formation.

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“…It was first reported by Bannister (1932) as being isomorphous with the structure of palladium sulphide and was named in honour of Sir William Henry Bragg and Professor William Lawrence Bragg as being the first new mineral to be discovered by X-ray methods alone. The structure of PdS was studied by Gaskell (1935) using singlecrystal photographic methods and the structure of braggite was inferred from this study.…”

Section: Introductionmentioning

confidence: 99%

The crystal structure of braggite, (Pt, Pd, Ni)S

Childs¹,

Hall²

1973

Acta Crystallogr Sect B

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The determination of the crystal structure of braggite by Patterson methods confirms the proposal of Gaskell [Z. Kristallogr. (1935) 96, 203-213], that braggite is isostructural with PdS. The cell dimensions are a= 6.380(1), e= 6.570(1) A, Z= 8 and the space group is P42/m. Full-matrix least-squares procedures were used with two sets of merged 4-circle diffractometer data to refine the atomic parameters to an R value of 0.068. Generalized absorption corrections were applied. Several different configurations of metal ordering were tested for the stoichiometric composition PtsPdzNiSs. It is proposed that the two Pd atoms preferentially occupy the site 2(d),(0,~-,1-), in the structure and that this is the minimum requirement in the formation of the PdS (braggite or vysotskite) structure rather than the PtS (cooperite) structure.

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Determination of minerals in platinum concentrates from the Transvaal by X-ray methods

Cited by 45 publications

References 6 publications

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

Compositional variation of cooperite, braggite, and vysotskite from the Bushveld Complex

The crystal structure of braggite, (Pt, Pd, Ni)S

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