IMA 2019-081 = alexkuznetsovite-(La); IMA 2019-118 = alexkuznetsovite-(Ce); IMA 2020-020 = biraite-(La)

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Marco E. Ciriotti
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IMA 2019-081 = alexkuznetsovite-(La); IMA 2019-118 = alexkuznetsovite-(Ce); IMA 2020-020 = biraite-(La)

Messaggio da Marco E. Ciriotti » mar 03 ago, 2021 14:11

Prossima pubblicazione.

Referenza:
▪ Kasatkin, A.V., Zubkova, N.V., Pekov, I.V., Chukanov, N.V., Škoda, R., Agakhanov, A.A., Belakovskiy, D.I., Britvin, S.N., Pushcharovsky, D.Yu. (2021): The mineralogy of the historical Mochalin Log REE deposit, South Urals, Russia. Part IV. Alexkuznetsovite-(La), La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce), Ce2Mn(CO3)(Si2O7), and biraite-(La), La2Fe2+(CO3)(Si2O7), three new isostructural minerals and a definition of the biraite group. Mineralogical Magazine, 85, (in press).

Abstract:
Three new isostructural minerals, alexkuznetsovite-(La), ideally La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce) Ce2Mn(CO3)(Si2O7), and biraite-(La) La2Fe2+(CO3)(Si2O7), were discovered in polymineralic nodules from the Mochalin Log REE deposit, South Urals, Russia. The new minerals form anhedral grains up to 0.3  0.4 mm [alexkuznetsovite-(La)], 0.5  0.9 mm [alexkuznetsovite-(Ce)] and 0.2  1.2 mm [biraite-(La)] embedded in granular aggregates consisting of different REE minerals [allanite-(Ce)/-(La), bastnäsite-(Ce)/-(La), fluorbritholite-(Ce), perbøeite-(Ce)/-(La), percleveite-(Ce)/-(La), törnebohmite-(Ce)/-(La) etc.]. All three new species are brown to dark brown, translucent in thin fragments, with white streak, vitreous lustre and Mohs’ hardness of ~5. Dcalc = 4.713 [alexkuznetsovite-(La)], 4.687 [alexkuznetsovite-(Ce)] and 4.682 [biraite-La)] g·cm–3. Their empirical formulae, calculated on the basis of 2 Si and 10 O apfu, are: alexkuznetsovite-(La): (La0.98Ce0.89Nd0.10Pr0.05)Σ2.02Mn2+0.50Fe2+0.29Ca0.12Mg0.03(CO3)0.94(HCO3)0.06 (Si2O7); alexkuznetsovite-(Ce): (Ce0.96La0.78Nd0.16Pr0.07)Σ1.97Th0.01Mn2+0.50Fe2+0.33Ca0.14Mg0.02(CO3)0.93 (HCO3)0.07(Si2O7); biraite-(La): (La0.95Ce0.87Nd0.08Pr0.04)Σ1.94Th0.01Ca0.12Fe2+0.44Mn2+0.38Mg0.07(CO3)0.88 (HCO3)0.12(Si2O7). The new minerals are monoclinic, P21/c and Z = 4. The unit-cell parameters of alexkuznetsovite-(La)/alexkuznetsovite-(Ce)/biraite-(La) are: a = 6.5642(3)/6.5764(4)/6.5660(10), b = 6.7689(3)/6.7685(4)/6.7666(11), c = 18.7213(10)/18.7493(15)/18.698(3) Å, β = 108.684(6)/108.672(8)/108.952(16)º, V = 788.00(7)/790.66(10)/785.7(2) Å3. The crystal structures are solved from single-crystal XRD data; R = 0.0628 [alexkuznetsovite-(La)], 0.0589 [alexkuznetsovite-(Ce)], and 0.1193 [biraite-(La)]. A new biraite group is defined; it includes isostructural biraite-(Ce) and the three new minerals described herein. The rootname alexkuznetsovite is given in honor of the Russian mineral collector Alexey M. Kuznetsov (born 1962) who provided samples in which all three new minerals were found. The Levinson's suffix-modifier -(La) or -(Ce) indicates the predominance of La or Ce among REE in the mineral. Biraite-(La) is named as an analogue of biraite-(Ce) with La prevailing among REE.
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: 31675
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2019-081 = alexkuznetsovite-(La); IMA 2019-118 = alexkuznetsovite-(Ce); IMA 2020-020 = biraite-(La)

Messaggio da Marco E. Ciriotti » ven 26 nov, 2021 16:00

Pubblicazione effettuata.

Referenza:
▪ Kasatkin, A.V., Zubkova, N.V., Pekov, I.V., Chukanov, N.V., Škoda, R., Agakhanov, A.A., Belakovskiy, D.I., Britvin, S.N., Pushcharovsky, D.Yu. (2021): The mineralogy of the historical Mochalin Log REE deposit, South Urals, Russia. Part IV. Alexkuznetsovite-(La), La2Mn(CO3)(Si2O7), alexkuznetsovite-(Ce), Ce2Mn(CO3)(Si2O7), and biraite-(La), La2Fe2+(CO3)(Si2O7), three new isostructural minerals and a definition of the biraite group. Mineralogical Magazine, 85, 772-783.
Marco E. Ciriotti

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