Manganese sturmanite from N’Chwaning 2 Mine (Kalahari, South Africa)

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Marco E. Ciriotti
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Manganese sturmanite from N’Chwaning 2 Mine (Kalahari, South Africa)

Messaggio da Marco E. Ciriotti » dom 12 giu, 2022 10:29

Referenza:
▪ Gritsenko, Yu.D., Dedushenko, S.K., Vigasina, M.F., Pautov, L.A., Golubev, Ya.V., Ogorodova, L.P., Ksenofontov, D.A., Melchakova, L.V., Perfilyev, Yu.D. (2022): Manganese Sturmanite from N’Chwaning 2 Mine (Kalahari, South Africa). Zapiski RMO, 151(2), 53-69.

Abstract non disponibile. Qui la traduzione:
For the first time, the method of iodometric titration was used to determine the oxidation state of manganese and the ratio Mn4+/Mn3+ (54/46%) in high-manganese sturmanite from the N’Chwaning 2 mine (Kalahari manganese ore field, South Africa). Mössbauer spectrum of sturmanite containing a single asymmetric Lorentzian doublet with the parameters RTISα-Fe = 0.31(1) mm/s, RTQS = 0.18(1) mm/s, FWHML= 0.55 mm/s and FWHMR = = 0.33 mm/s confirms the presence of iron in composition of the mineral only in the oxidation state +3. The process of thermal transformation of the mineral has been studied by thermal analysis and IR absorption spectroscopy: dehydration and destruction of calcium polyhedra occur up to 200 °C, dehydroxylation – up to 600 °C, decarbonatization – up to 750 °C, complete destruction of the structure with formation of anhydrite, hematite, calcium borates occurs up to 1000 °C. The chemical formula of the studied sturmanite, calculated according to investigation results for 8 cations, has the form Ca5.94Fe3+1.03Mn4+0.54Mn3+0.44Al0.03Si0.02[B(OH)4]1.00[B(OH)3]0.11[SO4]2.32[СО3]0.49(OH)12∙22.7H2O.
Marco E. Ciriotti

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