Röentgenite-(CE) and other ree fluorcarbonates from vein no. 35, Vishnevye mountains, Southern Urals

Abstract

A mineral assemblage including REE fuorcarbonates (röntgenite-(Ce) Ca2Ce3(CO3)5F3, parisite-(Ce) CaCe2(CO3)3F2, synchisite-(Ce) CaCe(CO3)2F and bastnäsite-(Ce) Ce(CO3)F) was discovered at the dumps of the Vein № 35 open pit, Mt. Dolgaya, Vishnevye Mountains, Southern Urals. These intimately intergrown minerals compose aggregates up to 1 mm in allanite-(Ce)/ferriallanite-(Ce) and chamosite and are associated with microcline, molybdenite, monazite-(Ce), pyrite, thorite, fuorite and fuorannite. The fnd of röntgenite-(Ce) is frst in Urals. Its empirical formula is: (Ca1.98Th0.03)Σ2.01 (Ce1.45La1.02Nd0.32Pr0.11Sm0.03Y0.02Gd0.02)Σ2.97(CO3)5[F2.48(OH)0.52)Σ3.00. The hexagonal unit cell dimensions of the mineral calculated from X-ray powder data are: a = 7.049(1) Å, c = 69.283(30) Å, V = 2981(1) ų. The strongest bands in the Raman spectrum of the mineral are 164, 250, 349, 606, 731, 867, 1091, 1451 and 1737 cm–1.