Informace o publikaci
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
| Autoři | |
|---|---|
| Rok publikování | 2021 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Mineralogical Magazine |
| Fakulta / Pracoviště MU | |
| Citace | |
| www | https://www.cambridge.org/core/journals/mineralogical-magazine/article/mineralogy-of-the-historical-mochalin-log-ree-deposit-south-urals-russia-part-iv-alexkuznetsovitela-la2mnco3si2o7-alexkuznetsovitece-ce2mnco3si2o7-and-biraitela-la2fe2co3si2o7-three-n |
| Doi | http://dx.doi.org/10.1180/mgm.2021.64 |
| Klíčová slova | alexkuznetsovite-(La); alexkuznetsovite-(Ce); biraite-(La); new mineral; rare-earth carbonate-silicate; crystal structure; biraite group; Mochalin Log; South Urals |
| Popis | 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 mm x 0.4 mm [alexkuznetsovite-(La)], 0.5 mm x 0.9 mm [alexkuznetsovite-(Ce)] and 0.2 mm x 1.2 mm [biraite-(La)] embedded in granular aggregates consisting of different REE minerals [allanite-(Ce)/-(La), bastnasite-(Ce)/-(La), fluorbritholite-(Ce), perbOeite-(Ce)/-(La), percleveite-(Ce)/-(La) and tornebohmite-(Ce)/-(La)]. All three new species are brown to dark brown, translucent in thin fragments, with white streak, vitreous lustre and Mohs' hardness of similar to 5. D-calc = 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)(Sigma 2.02)Mn0.502+Fe0.292+Ca0.12Mg0.03(CO3)(0.94)(HCO3)(0.06) (Si2O7); alexkuznetsovite-(Ce): (Ce0.96La0.78Nd0.16Pr0.07)(Sigma 1.97)Th0.01Mn0.502+Fe0.332+Ca0.14Mg0.02(CO3)(0.93)(HCO3)(0.07)(Si2O7); and biraite-(La): (La0.95Ce0.87Nd0.08Pr0.04)(Sigma 1.94)Th0.01Ca0.12Fe0.442+Mn0.382+Mg0.07(CO3)(0.88)(HCO3)(0.12)(Si2O7). The new minerals are monoclinic, P2(1)/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) angstrom, beta = 108.684(6)/108.672(8)/108.952(16)degrees and V = 788.00(7)/790.66(10)/785.7(2) angstrom(3). The crystal structures are solved from single-crystal X-ray diffraction 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 honour 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. |