IMA 2023-A = discreditation of platarsite: A S-rich variety of sperrylite

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Marco E. Ciriotti
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IMA 2023-A = discreditation of platarsite: A S-rich variety of sperrylite

Messaggio da Marco E. Ciriotti » mer 13 set, 2023 21:13

Prossima pubblicazione.

Referenza:
▪ Mcdonald, A.M & Cabri, L.J. (2023): Discreditation of Platarsite: A S-Rich Variety of Sperrylite. The Canadian Journal of Mineralogy and Petrology, 61, (in press).

Abstract:
Platarsite is a relatively uncommon platinum-group mineral, reported from several world-wide localities, that has been defined as both Pt(As,S)2 and PtAsS in the literature. It was first described using material from the Onverwacht mine, eastern Bushveld Complex, Republic of South Africa, where it occurs with genkinite, geversite, and Pt-Fe alloy. Data from chemical analyses indicate (1) Pt is the dominant PGE, but with significant enrichments of both Rh and Ru; (2) ΣAs+S ∼ 2; (3) ΣPGE:ΣAs+S ∼ 1:2; and (4) As:S ratios of ∼1 (but with most data showing As > S), all of which suggest either PtAsS or Pt(As,S)2 as ideal compositions. Results from crystal-structure analyses conducted on both platarsite and sperrylite (Szymański 1979) demonstrate that the two are isostructural, both crystallizing in the cubic space group Pa3, with refined unit-cell edges of 5.788(1) and 5.9681(1) Å, respectively. They possess a pyrite-like crystal structure that includes a single metal site and a single anion site. The latter indicates that As and S, even if present in ratios of ∼1, must be disordered over a single site, rather than occupying two separate crystallographic sites. A re-evaluation of the available chemical data, along with the results from crystal-structure analyses, indicate that platarsite is a S-enriched variety of sperrylite and, as such, it has been discredited as a valid mineral species.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 31313
Iscritto il: ven 25 giu, 2004 11:31
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Re: IMA 2023-A = discreditation of platarsite: A S-rich variety of sperrylite

Messaggio da Marco E. Ciriotti » dom 15 ott, 2023 10:13

Pubblicazione effettuata.

Referenza:
▪ Mcdonald, A.M & Cabri, L.J. (2023): Discreditation of Platarsite: A S-Rich Variety of Sperrylite. The Canadian Journal of Mineralogy and Petrology, 61, 1039-1044.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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