IMA 2017-024 = somersetite

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Marco E. Ciriotti
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IMA 2017-024 = somersetite

Messaggio da Marco E. Ciriotti » ven 18 mag, 2018 18:18

Prossima pubblicazione.

Referenza:
▪ Siidra, O.I., Nekrasova, D.O., Turner, R., Zaitsev, A.N., Chukanov, N.V., Polekhovsky, Y.S., Spratt, J., Rumsey, M.S. (2018): Somersetite, Pb8O(OH)4(CO3)5, a New Complex Hydrocerussite-Related Mineral from the Mendip Hills. Mineralogical Magazine, 82, (in press).
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: 24920
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: IMA 2017-024 = somersetite

Messaggio da Marco E. Ciriotti » ven 09 nov, 2018 20:28

Pubblicazione effettuata.

Referenza:
▪ Siidra, O.I., Nekrasova, D.O., Turner, R., Zaitsev, A.N., Chukanov, N.V., Polekhovsky, Y.S., Spratt, J., Rumsey, M.S. (2018): Somersetite, Pb8O(OH)4(CO3)5, a New Complex Hydrocerussite-Related Mineral from the Mendip Hills. Mineralogical Magazine, 82, 1211-1224.

Abstract:
The new mineral somersetite, has been found at Torr Works (‘Merehead quarry’) in Somerset, England, United Kingdom. Somersetite is green or white (typically it is similar visually to hydrocerussite-like minerals but with a mint-green tint), forms plates and subhedral grains up to 5 mm across and up to 2 mm thick. In bi-coloured crystals it forms very thin intergrowths with plumbonacrite. The empirical formula of somersetite is Pb8.00C5.00H4.00O20. The simplified formula is Pb8O(OH)4(CO3)5, which requires: PbO = 87.46, CO2 = 10.78, H2O = 1.76, total 100.00 wt.%.
The infrared spectrum of somersetite is similar to that of plumbonacrite and, to a lesser degree, hydrocerussite. Somersetite is hexagonal, P63/mmc, a = 5.2427(7), c = 40.624(6) Å, V = 967.0(3) Å3 and Z = 2. The eight strongest reflections of the powder X-ray diffraction (XRD) pattern [d,Å(I)(hkl)] are: 4.308(33)(103), 4.148(25)(104), 3.581(40)(107), 3.390(100)(108), 3.206(55)(109), 2.625(78)(110), 2.544(98)(0.0.16) and 2.119(27)(1.0.17). The crystal structure was solved from single-crystal XRD data giving R1 = 0.031. The structure of somersetite is unique and consists of the alternation of the electroneutral plumbonacrite-type [Pb5O(OH)2(CO3)3]0 and hydrocerussite-type [Pb3(OH)2(CO3)2]0 blocks separated by stereochemically active lone electron pairs on Pb2+. There are two blocks of each type per unit cell in the structure, which corresponds to the formula [Pb5O(OH)2(CO3)3][Pb3(OH)2(CO3)2] or Pb8O(OH)4(CO3)5 in a simplified representation. The 2D blocks are held together by weak Pb–O bonds and weak interactions between lone pairs.
Marco E. Ciriotti

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