New data on Bi, Pb-bearing and Mn-rich gem tourmaline from Malkhan Pegmatite District

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Marco E. Ciriotti
Messaggi: 30242
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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New data on Bi, Pb-bearing and Mn-rich gem tourmaline from Malkhan Pegmatite District

Messaggio da Marco E. Ciriotti » gio 01 dic, 2022 9:31

Referenza:
▪ Vereshchagin, O.S., Kasatkin, A.V., Škoda, R. (2022): New data on Bi, Pb-bearing and Mn-rich gem tourmaline from the Malkhan Pegmatite District (transbaikalia). Zapiski RMO, 151, 46-57.

Abstract:
Lead or/and Bi-bearing tourmalines are rare in nature while Mn-bearing ones are quite common. Here, we present new data on Bi-(up to ~2 wt % Bi 2 O 3), Pb-bearing (up to ~2 wt % PbO) and Mn-rich (up to ~5 wt % MnO) tourmalines from the Irkutianka vein and Mn-rich tour-malines (up to ~6.5 wt % MnO) from the Novaya vein, both occurring at the Malkhan peg-matite district. Four gem-quality tourmalines (sm21-1, sm21-2, sm21-3, and sm21-4) of different color (yellow, colorless and red) and morphology (elongated and flattened) from the Irkutianka vein were studied by optical and scanning electron microscopy (SEM) and energy dispersive analysis (EDS). Two samples (1015f and 1377f) of gemmy yellow tourmaline from the Novaya vein were additionally examined using WDS and LA-ICP-MS. All the studied tourmalines from the Irkutianka vein belong to fluor-elbaite-fluor-liddicoatite series and show the Na/Ca and Li/Mn/Fe zonation. The tourmalines from the Novaya vein, instead, do not show any zonation and belong to Mn-rich (up to 0.88 apfu Mn) fluor-elbaite. The complex chemical zonation observed for transitional metal contents resulted in the appearance of color (or a lack of it). Colorless tourmaline sm21-4 has constant Bi impurity, whose amount decreases from the rim to the core (from 0.09 to 0.01 apfu) of the crystal in question. This tourmaline is among the Bi-richest species discovered so far. Lead was detected in rose-to-colorless tourmaline sm21-3 and colorless one sm21-4. Only the inner parts of the tour-maline sm21-3 contain lead (<0.2 wt % PbO), while the Pb-richest domains (up to 30 mμ in size; Pb up to 0.09 apfu) were discovered in the core of the tourmaline sm21-4. We suppose that both Pb 2+ and Bi 3+ occupy the nine-coordinated X-site in the tourmaline crystal structure.
Marco E. Ciriotti

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Ferdinando Giovine
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Re: New data on Bi, Pb-bearing and Mn-rich gem tourmaline from Malkhan Pegmatite District

Messaggio da Ferdinando Giovine » gio 01 dic, 2022 12:52

Ciao, hai la copia? Grazie.

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