Informace o publikaci
The mineralogy of the historical Mochalin Log REE deposit, South Urals, Russia. Part V. Zilbermintsite-(La), (CaLa5)(Fe3+Al3Fe2+)[Si2O7][SiO4]5O(OH)3, a new mineral with ET2 type structure and a definition of the radekškodaite group
| Autoři | |
|---|---|
| Rok publikování | 2024 |
| 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-v-zilbermintsitela-cala5fe3al3fe2si2o7sio45ooh3-a-new-mineral-with-et2-type-structure-and-a-definition-of |
| Doi | http://dx.doi.org/10.1180/mgm.2024.17 |
| Klíčová slova | zilbermintsite-(La); new mineral; crystal structure; ET2 type; radek & scaron;kodaite group; Mochalin Log; South Urals |
| Popis | The new mineral zilbermintsite-(La), ideally (CaLa5)(Fe3+Al3Fe2+)[Si2O7][SiO4](5)O(OH)(3), was found in a single polymineralic nodule from the Mochalin Log REE deposit, Chelyabinsk Oblast, South Urals, Russia. Zilbermintsite-(La) forms anhedral grains up to 0.65 x 0.20 mm at the contact of ferriperb & oslash;eite-(La), t & ouml;rnebohmite-(La) and ferriallanite-(Ce). Other associated minerals include bastn & auml;site-(La), biraite-(La), ferriallanite-(La), ferriperb & oslash;eite-(Ce), fluorbritholite-(Ce), monazite-(La), perb & oslash;eite-(La), percleveite-(Ce), percleveite-(La), perrierite-(Ce), perrierite-(La), thorianite, thorite and quartz. The new mineral is light brown, translucent in thin fragments with a vitreous lustre. It is brittle, with good {100} cleavage. Mohs hardness is ca. 6. D-calc = 4.684 g cm(-3). Optically, zilbermintsite-(La) is biaxial (+), alpha = 1.805(7), beta = 1.812(7) and gamma = 1.867(8) (589 nm); 2V(meas) = 40(15)degrees and 2V(calc) = 40 degrees. The empirical formula based on O-28(OH,F)(3) apfu is (Ca0.94La2.56Ce2.18Nd0.20Pr0.10Th0.02)(Sigma 6.00)(Al2.96Fe0.903+Fe0.642+Mg0.34Mn0.13Ti0.03)(Sigma 5.00)Si7.00O28[(OH)(2.42)F-0.58]. Zilbermintsite-(La) is monoclinic, P2(1)/m; the unit-cell parameters are: a = 8.9605(5), b = 5.7295(2), c = 25.1033(13) & Aring;, beta = 116.616(7), V = 1152.21(12) & Aring;(3) and Z = 2. The crystal structure of zilbermintsite-(La) is solved from the single-crystal X-ray diffraction data [R = 0.0757 for 2857 unique reflections with I > 2 sigma(I)]. The new mineral is isotypic to radek & scaron;kodaite-(La) and radek & scaron;kodaite-(Ce) and together with them forms the newly defined radek & scaron;kodaite group. All members of this group possess the ET2 type structure where one epidote-type module (E) regularly alternates with two t & ouml;rnebohmite-type modules (T). The new mineral honours Professor Veniamin A. Zilbermints (1887-1939) who was a pioneer of the study of the Mochalin Log deposit. The Levinson suffix-modifier -(La) indicates the predominance of La among rare-earth elements in the mineral. |