• journal_title：American Mineralogist
• Contributor：Irina O. Galuskina ; Evgeny V. Galuskin ; Thomas Armbruster ; Biljana Lazic ; Joachim Kusz ; Piotr Dzierżanowski ; Viktor M. Gazeev ; Nikolai N. Pertsev ; Krystian Prusik ; Aleksandr E. Zadov ; Antoni Winiarski ; Roman Wrzalik ; Anatoly G. Gurbanov
• Publisher：Mineralogical Society of America
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2010.3507
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：95
• issue：8-9
• firstpage：1172
• section：Articles

Elbrusite-(Zr) Ca₃(U⁶⁺Zr)(Fe³⁺₂Fe²⁺)O₁₂, a new uranian garnet (Ia<ovl>3</ovl>d, a ≈ 12.55 Å, V ≈ 1977 ų, Z = 8), within the complex solid solution elbrusite-kimzeyite-toturite Ca₃(U,Zr,Sn,Ti,Sb,Sc,Nb...)₂(Fe,Al,Si,Ti)₃O₁₂ was discovered in spurrite zones in skarn xenoliths of the Upper Chegem caldera. The empirical formula of holotype elbrusite-(Zr) with 25.14 wt% UO₃ is (Ca_3.040Th_0.018Y_0.001) _∑3.059(U⁶⁺_0.658Zr_1.040Sn_0.230 Hf_0.009Mg_0.004) _∑1.941 (Fe³⁺_1.575Fe²⁺_0.559Al_0.539 Ti⁴⁺_0.199Si_0.099Sn_0.025V⁵⁺_0.004) _∑3O₁₂. Associated minerals are spurrite, rondorfite, wadalite, kimzeyite, perovskite, lakargiite, ellestadite-(OH), hillebrandite, afwillite, hydrocalumite, ettringite group minerals, and hydrogrossular. Elbrusite-(Zr) forms grains up to 10–15 μm in size with dominant {110} and minor {211} forms. It often occurs as zones and spots within Fe³⁺-dominant kimzeyite crystals up to 20–30 μm in size. The mineral is dark-brown to black with a brown streak. The density calculated on the basis of the empirical formula is 4.801 g/cm³ The following broad bands are observed in the Raman spectra of elbrusite-(Zr): 730, 478, 273, 222, and 135 cm⁻¹. Elbrusite-(Zr) is radioactive and nearly completely metamict. The calculated cumulative dose (α-decay events/mg) of the studied garnets varies from 2.50 × 10¹⁴ [is equivalent to 0.04 displacement per atom (dpa)] for uranian kimzeyite (3.36 wt% UO₃), up to 2.05 × 10¹⁵ (0.40 dpa) for elbrusite-(Zr) with 27.09 wt% UO₃.