SAAMITE, Ba TiNbNa3Ti(Si2O7)2O2(OH)2(H2O)2, A GROUP-III Ti-DISILICATE MINERAL FROM THE KHIBINY ALKALINE MASSIF, KOLA PENINSULA, RUSSIA: DESCRIPTION AND CRYSTAL STRUCTURE

2014 ◽  
Vol 52 (4) ◽  
pp. 745-762 ◽  
Author(s):  
F. Camara ◽  
E. Sokolova ◽  
Y. A. Abdu ◽  
F. C. Hawthorne
2009 ◽  
Vol 428 (1) ◽  
pp. 1051-1053 ◽  
Author(s):  
A. A. Grigorieva ◽  
N. V. Zubkova ◽  
I. V. Pekov ◽  
D. Yu. Pushcharovsky

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 219
Author(s):  
Victor Yakovenchuk ◽  
Yakov Pakhomovsky ◽  
Taras Panikorovskii ◽  
Andrey Zolotarev ◽  
Julia Mikhailova ◽  
...  

Chirvinskyite, (Na,Ca)13(Fe,Mn,□)2(Ti,Nb)2(Zr,Ti)3(Si2O7)4(OH,O,F)12, is a new wöhlerite–related zirconotitano–sorosilicate. It is triclinic, P1, a = 7.0477(5), b = 9.8725(5), c = 12.2204(9) Å, α = 77.995(5), β = 82.057(6), γ = 89.988(5)°, V = 823.35(9) Å3, Z = 1. The mineral was found in albitized alkaline pegmatites in a foyaite of the Mt. Takhtarvumchorr (Khibiny alkaline massif, Kola Peninsula, Russia, N 67°40’, E 33°33’). Chirvinskyite forms sheaf–like and radiated aggregates (up to 6 mm in diameter) of split fibrous crystals hosted by saccharoidal fluorapatite and albite. The mineral is pale cream in color, with a silky luster and a white streak. The cleavage is not recognized. Mohs hardness is 5. Chirvinskyite is biaxial (–), α 1.670(2), β 1.690(2), γ 1.705(2) (589 nm), 2Vcalc = 80.9°. The calculated and measured densities are 3.41 and 3.07(2) g·cm−3, respectively. The empirical formula based on Si = 8 apfu is (Na9.81Ca3.28K0.01)∑13.10(Fe0.72Mn0.69□0.54Mg0.05)∑2.00 (Ti1.81Nb0.19)∑2.00(Zr2.27Ti0.63)∑2.90(Si2O7)4{(OH)5.94O3.09F2.97}∑12.00. Chirvinskyite belongs to a new structure type of minerals and inorganic compounds and is related to the wöhlerite-group minerals. Its modular “wallpaper” structure consists of disilicate groups Si2O7 and three types of “octahedral walls”. The mineral is named in honor of Petr Nikolaevich Chirvinsky (1880–1955), Russian geologist and petrographer, head of the Petrography Department of the Perm’ State University (1943–1953), for his contributions to mineralogy and petrology, including studies of the Khibiny alkaline massif.


2014 ◽  
Vol 78 (3) ◽  
pp. 483-496 ◽  
Author(s):  
V. N. Yakovenchuk ◽  
S.V. Krivovichev ◽  
G. Y. Ivanyuk ◽  
Ya. A. Pakhomovsky ◽  
E.A. Selivanova ◽  
...  

AbstractKihlmanite-(Ce), Ce2TiO2[SiO4](HCO3)2(H2O), is a new rare-earth titanosilicate carbonate, closely related to tundrite-(Ce). It is triclinic, P, a = 4.994(2), b = 7.54(2), c = 15.48(4) Å, α = 103.5(4), β = 90.7(2), γ = 109.2(2)o , V = 533(1) Å3, Z = 2 (from powder diffraction data) or a = 5.009(5), b = 7.533(5), c = 15.407(5) Å, α = 103.061(5), β = 91.006(5), γ = 109.285(5)°, V = 531.8(7) Å3, Z = 2 (from single-crystal X-ray diffraction data). The mineral was found in the arfvedsonite-aegirine-microcline vein in fenitized metavolcanic rock at the foot of the Mt Kihlman (Chil’man), near the western contact of the Devonian Khibiny alkaline massif and the Proterozoic Imandra-Varzuga greenstone belt. It forms brown spherulites (up to 2 cm diameter) and sheaf-like aggregates of prismatic crystals, flattened on {010} and up to 0.5 mm diameter. Both spherulites and aggregates occur in interstices in arfvedsonite and microcline, in intimate association with golden-green tundrite-(Ce). Kihlmanite-(Ce) is brown, with a vitreous lustre and a pale yellowish-brown streak. The cleavage is perfect on {010}, parting is perpendicular to c and the fracture is stepped. Mohs hardness is ∼3. In transmitted light, the mineral is yellowish brown; pleochroism and dispersion were not observed. Kihlmanite-(Ce) is biaxial (+), α = 1.708(5), β = 1.76(1), γ = 1.82(1) (589 nm), 2Vcalc = 89°. The optical orientation is Y ^ c = 5°, other details are unclear. The calculated and measured densities are 3.694 and 3.66(2) g cm−3, respectively. The mean chemical composition, determined by electron microprobe, is: Na2O 0.13, Al2O3 0.24, SiO2 9.91, CaO 1.50, TiO2 11.04, MnO 0.26, Fe2O3 0.05, Nb2O5 2.79, La2O3 12.95, Ce2O3 27.33, Pr2O3 2.45, Nd2O3 8.12, Sm2O3 1.67, Gd2O3 0.49 wt.%, with CO2 15.0 and H2O 6.0 wt.% (determined by wet chemical and Penfield methods, respectively), giving a total of 99.93 wt.%. The empirical formula calculated on the basis of Si + Al = 1 atom per formula unit is (Ca0.16Na0.11Mn0.02)∑0.29[(Ce0.98La0.47Pr0.09Nd0.29Sm0.06Gd0.02)∑1.91(Ti0.82Nb0.12)∑0.94O2 (Si0.97Al0.03)∑1O4.02(HCO3)2.01](H2O)0.96. The simplified formula is Ce2TiO2(SiO4)(HCO3)2·H2O. The mineral reacts slowly in cold 10% HCl with weak effervescence and fragmentation into separate plates. The strongest X-ray powder-diffraction lines [listed as d in Å(I) (hkl)] are as follows: 15.11(100)(00), 7.508(20)(00), 6.912(12)(01), 4.993(14)(00), 3.563(15)(01), 2.896(15)(1). The crystal structure of kihlmanite-(Ce) was refined to R1 = 0.069 on the basis of 2441 unique observed reflections (MoKα, 293 K). It is closely related to the crystal structure of tundrite-(Ce) and is based upon [Ce2TiO2(SiO4)(HCO3)2] layers parallel to (001). Kihlmanite-(Ce) can be considered as a cationdeficient analogue of tundrite-(Ce). The mineral is named in honour of Alfred Oswald Kihlman (1858–1938), a remarkable Finnish geographer and botanist who participated in the Wilhelm Ramsay expeditions to the Khibiny Mountains in 1891–1892. The mineral name also reflects its occurrence at the Kihlman (Chil’man) Mountain.


2007 ◽  
Vol 92 (2-3) ◽  
pp. 416-423 ◽  
Author(s):  
V. N. Yakovenchuk ◽  
S. V. Krivovichev ◽  
Y. A. Pakhomovsky ◽  
G. Yu. Ivanyuk ◽  
E. A. Selivanova ◽  
...  

2017 ◽  
Vol 81 (6) ◽  
pp. 1533-1550 ◽  
Author(s):  
E. Sokolova ◽  
A. Genovese ◽  
A. Falqui ◽  
F.C. Hawthorne ◽  
F. Cámara

AbstractThe crystal structure and chemical formula of zvyaginite, ideally Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a lamprophyllite-group mineral of the seidozerite supergroup from the type locality, Mt. Malyi Punkaruaiv, Lovozero alkaline massif, Kola Peninsula, Russia have been revised. The crystal structurewas refined with a new origin in space group C1, a = 10.769(2), b = 14.276(3), c = 12.101(2) Å, α = 105.45(3), β = 95.17(3), γ = 90.04(3)°, V = 1785.3(3.2) Å3, R1 = 9.23%. The electron-microprobe analysis gave the following empirical formula [calculated on 22 (O + F)]: (Na0.75Ca0.09K0.04□1.12)Σ2 (Na1.12Zn0.88Mn0.17Fe2+0.04□0.79)Σ3 (Nb1.68Ti1.25Al0.07)Σ3 (Si4.03O14)O2 [(OH)1.11F0.89]Σ2(H2O)4, Z = 4. Electron-diffraction patterns have prominent streaking along c* and HRTEM images show an intergrowth of crystalline zvyaginite with two distinct phases, both of which are partially amorphous. The crystal structure of zvyaginite is an array of TS (Titanium-Silicate) blocks connected via hydrogen bonds between H2O groups. The TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the [6]MO(1,4,5) sites are occupied mainly by Ti, Zn and Na and the [6]MO(2,3) sites are occupied by Na at less than 50%. In the H sheet, the [6]MH(1,2) sites are occupied mainly by Nb and the [8]AP(1) and [8]AP(2) sites are occupied mainly by Na and □. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula is Na□Nb2NaZn□Ti(Si2O7)2O2(OH)2(H2O)4. Zvyaginite is a Zn-bearing and Na-poor analogue of epistolite, ideally (Na□)Nb2Na3Ti(Si2O7)2O2(OH)2(H2O)4. Epistolite and zvyaginite are related by the following substitution in the O sheet of the TS-block: (Naþ 2 )epi↔Zn2+ zvy +□zvy. The doubling of the t1 and t2 translations of zvyaginite relative to those of epistolite is due to the order of Zn and Na along a (t1) and b (t2) in the O sheet of zvyaginite.


2017 ◽  
Vol 81 (1) ◽  
pp. 175-181 ◽  
Author(s):  
Elena Sokolova ◽  
Fernando Cámara ◽  
Frank C. Hawthorne ◽  
Evgeny I. Semenov ◽  
Marco E. Ciriotti

AbstractLobanovite, K2Na(Fe42+Mg2Na)Ti2(Si4O12)2O2(OH)4, is a new mineral of the astrophyllite supergroup from Mt. Yukspor, the Khibiny alkaline massif, Kola Peninsula Russia. It has been known previously under the following names: monoclinic astrophyllite, magnesium astrophyllite, magnesiumastrophyllite and magnesioastrophyllite but has never been formally proposed and approved as a valid mineral species by the Commission on new Minerals, Nomenclature and Classification of the International Mineralogical Association. It has now been revalidated and named lobanovite after Dr. Konstantin V. Lobanov, a prominent Russian ore geologist who worked in the Kola Peninsula for more than forty years (Nomenclature voting proposal 15-B). Lobanovite has been described from pegmatitic cavities on Mt. Yukspor where it occurs as elongated bladed crystals, up to 0.04 mm wide and 0.2 mm long, with a straw yellow to orange colour. Associated minerals are shcherbakovite, lamprophyllite, delindeite, wadeite, umbite and kostylevite. Lobanovite is biaxial (–) with refractive indices (λ = 589 nm) α = 1.658, βcalc. = 1.687, γ = 1.710; 2Vmeas. = 81.5– 83°. Lobanovite is monoclinic, space group C2/m, a = 5.3327(2), b = 23.1535(9), c = 10.3775(4) Å, β = 99.615(1)°, V = 1263.3 (1) Å 3, Z = 2. The six strongest reflections in the powder X-ray diffraction data [d (Å), I, (hkl)] are: 3.38, 100, (003); 2.548, 90, (063); 10.1, 80, (001); 3.80, 60, (042,131); 3.079, 50, (132,062); 2.763, 90, (1̄71). The chemical composition of lobanovite was determined by electron-microprobe analysis and the empirical formula (K1.97Ba0.01)∑1.98(Na0.65Ca0.14)∑0.79 (Fe3.182+Mg2.02Na1.00Mn0.72)∑6.92(Ti1.99Nb0.06)∑2.05[(Si8.01Al0.06)∑8.07O24]O2(OH)4.03F0.19 was calculated on the basis of 30.2 (O + OH + F) anions, with H2O calculated from structure refinement, Dcalc. = 3.161 g cm–3. In the structure of lobanovite, the main structural unit is the HOH block, which consists of one close-packed O (Octahedral) and two H (Heteropolyhedral) sheets. The M(1–4) octahedra form the O sheet and the T4O12 astrophyllite ribbons and [5]-coordinated Ti-dominant D polyhedra link through common vertices to form the H sheet. The HOH blocks repeat along [001], and K and Na atoms occur at the interstitial A and B sites. The simplified and end-member formulae of lobanovite are K2Na [(Fe2+,Mn)4Mg2Na]Ti2(Si4O12)2O2(OH)4 and K2Na(Fe42+Mg2Na)Ti2(Si4O12)2O2(OH)4, respectively.


2010 ◽  
Vol 74 (5) ◽  
pp. 821-832 ◽  
Author(s):  
S. V. Krivovichev ◽  
V. N. Yakovenchuk ◽  
E. S. Zhitova ◽  
A. A. Zolotarev ◽  
Y. A. Pakhomovsky ◽  
...  

AbstractThe crystal structure of quintinite-2H-3c, [Mg4Al2(OH)12](CO3)(H2O)3, from the Kovdor alkaline massif, Kola peninsula, Russia, was solved by direct methods and refined to an agreement index (R1) of 0.055 for 484 unique reflections with |Fo| ≥ 4σF. The mineral is rhombohedral, R32, a = 5.2745(7), c = 45.36(1) Å. The diffraction pattern of the crystal has strong and sharp Bragg reflections having h–k = 3n and l = 3n and lines of weak superstructure reflections extended parallel to c* and centred at h–k ≠ 3n. The structure contains six layers within the unit cell with the layer stacking sequence of …AC=CA=AC=CA=AC=CA… The Mg and Al atoms are ordered in metal hydroxide layers to form a honeycomb superstructure. The full superstructure is formed by the combination of two-layer stacking sequence and Mg-Al ordering. This is the first time that a long-range superstructure in carbonate-bearing layered double hydroxide (LDH) has been observed. Taking into account Mg-Al ordering, the unique layer sequence can be written as …=Ab1C=Cb1A=Ab2C=Cb2A=Ab3C=Cb3A=… The use of an additional suffix is proposed in order to distinguish between LDH polytypes having the same general stacking sequence but with different c parameters compared with the ‘standard’ polytype. According to this notation, the quintinite studied here can be described as quintinite-2H-3c or quintinite-2H-3c[6R], indicating the real symmetry.


2002 ◽  
Vol 40 (3) ◽  
pp. 961-970 ◽  
Author(s):  
A. P. Khomyakov ◽  
G. N. Nechelyustov ◽  
E. Sokolova ◽  
E. Bonaccorsi ◽  
S. Merlino ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document