Manaevite-(Ce), a new vesuvianite-group mineral has been investigated by means of electron microprobe, TGA and DSC and CHN analysis of H2O, powder X-ray diffraction, single-crystal X-ray structure analysis, 139La NMR, 57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are a = 15.9247(13) Å, c = 11.9661(10) Å, space group P4/nnc. The structure model was solved and refined to R1 = 3.35% for 1757 independent observed reflections with I > 4σ(I). Manaevite-(Ce) is the first vesuvianite-group mineral with the species-defining role of REE3+ at the X3 site. The mineral contains two different kinds of hydroxyl anions. The first type of hydroxyl groups is associated with the O10 and O11 sites as observed for other vesuvianite-group members. Another type of OH groups is due to the hydrogarnet substitution (H4O4)4‒ ↔ (SiO4) 4‒ associated with the Z1 and Z2 sites. The incorporation of REE3+ into the crystal structure of manaevite-(Ce) proceeds via the substitution schemes 2Ca2+  ↔ Th4+ + □ and 3Ca2+  ↔ 2REE3+ + □, which results in the formation of vacancies at the X3 site and the presence of H2O molecules.

Статья представлет собой сводку основных научных результатов сотрудников Минералогического музея им. А.Е. Ферсмана РАН (Минмузея РАН) за 2018 год. Приведены краткие описания 31 нового минерального вида: хреновит, рабдоборит-(V), рабдоборит-(W), манаевит-(Ce), параберцелиит, белогубит, зубковаит, ахирофанит, алеутит, эласмохлоит, ханауэрит, удинаит, арсенудинаит, акоповаит, феррипербёит-(La), радекшкодаит-(La), гладковскиит, феррьерит, дальнегорскит, красноштейнит, антофагастаит, плиниусит, яржемскиит, алексхомяковит, миланридерит, круйенит, фальгарит, бадахшанит-(Y), наталиякуликит, авдеевит, пербёит-(La). Суммированы текущие результаты минералогического изучения Архангельской алмазоносной провинции, пегматитов Памира, фумарол Толбачинского дола и возгонов угольных пожаров Равата, редкоземельной минерализации Мочалиного Лога и таллиевой минерализации Воронцовского месторождения на Урале. Приведены результаты изучения оливина магнезиальных скарнов и редких для магматических пород находок экстремально магнезиального оливина (Fo96) и оливина, содержащего до 0.48 мас. P2O5. В оливине магнезиальных скарнов впервые зафиксировано существенное содержание титана. Суммированы данные по составу включений хромшпинелида в оливине из вулканических пород Камчатки.

Cymrite, BaAl2Si2O8 · nH2O, is a rare mineral formed during low-grade dynamothermal metamorphism (T = 250–300°C, P = 1–3 kbar). Cymrite has been described from many metasedimentary ores and hydrothermal rocks. In carbonatites, it has been found for the first time. Cymrite has been identified in the Kovdor and Seblyavr massifs, Kola Peninsula. In Kovdor, this mineral has been described from one of the hydrothermal veins cutting the pyroxenite-melilitite-ijolite complex at the Phlogopite deposit; cymrite is associated with thomsonite, calcite, and stivensite. In the Seblyavr pluton, cymrite occurs in thin veins of calcite carbonatite that cut pyroxenite contacting with ijolite. Cymrite from the Seblyavr pluton is associated with calcite, natrolite, pyrite, and chalcopyrite. The mineral is optically negative and uniaxial, with extinction parallel to elongation; ω ∼ 1.607(1). According to X-ray diffraction data, cymrite from Seblyavr is monoclinic, space group P1m1; unit-cell dimensions are: a = 5.33, b = 36.96, c = 7.66 Å, β = 90°, V = 1510.55 Å3. According to the results of IR spectroscopy, in the series of samples from different massifs (in the running order Kovdor-Voishor-Seblyavr), the double-layer deformation is enhanced and accompanied by a decrease in the Si-O-Si angle and weakening of hydrogen bonds of interlayer water. The empirical formulas of cymrite calculated from electron microprobe analyses are Ba0.93–0.95Ca0.01–0.02K0.00–0.05Na0.02–0.04Al1.97–2.01Si1.99–2.03O8(H2O) and Ba1.00–1.02Ca0.00–0.01Sr0.00–0.01Fe0.00–0.01Al1.94–2.00Si1.98–2.03O8(H2O) at Seblyavr and Kovdor, respectively. Cymrite from the carbonatite massifs of the Kola Peninsula was formed under hydrothermal conditions at low temperature (200–300°C), high activity of Ba and Si, and high water pressure. At Kovdor, the mineral crystallized directly from the residual solution enriched in Ba. The sequence of mineral deposition is as follows: thomsonite-cymrite-calcite-stevensite. Cymrite from the Seblyavr pluton is a product of hydrothermal alteration of primary Na-K-Ba silicates of ijolite: nepheline, feldspar, and probably celsian. Natrolite replaces cymrite indicating high alkalinity of late hydrothermal fluids.