From structure topology to chemical composition. IX. Titanium silicates: revision of the crystal chemistry of lomonosovite and murmanite, Group-IV minerals

Cámara, Fernando; Sokolova, Elena; Hawthorne, Frank C.; Abdu, Yassir A.

doi:10.1180/minmag.2008.072.6.1207

Cited by 32 publications

(29 citation statements)

References 16 publications

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“…The crystal structure of murmanite was first examined by Khalilov et al (1965) and repeatedly refined later, with space groups P-1 and P1 (Rastsvetaeva & Andrianov, 1986;Khalilov, 1989;Nemeth et al, 2005, andCámara et al, 2008, who reviewed this history). The structural data on murmanite from the Severnyi open pit, Lovozero, the material source for our ion-exchange experiments, were reported by Lykova et al (2015).…”

Section: Crystal Structures: Description and Discussionmentioning

confidence: 99%

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Lykova¹,

Pekov²,

Zubkova³

et al. 2015

ejm

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The crystal structure of vigrishinite, an epistolite-group heterophyllosilicate with essential Zn, has been reinvestigated; the ideal end-member formula is revised to Zn 2 Ti 4-x (Si 2 O 7) 2 O 2 (OH,F,O) 2 (H 2 O,OH,&) 4 with x,1. Structure models of Zn-exchanged forms of murmanite after 5 and 24 hour experiments with 1N ZnSO 4 solution at 90 C have been obtained from single-crystal X-ray diffraction data. The structural formulae are [B1] Ca 0.04 {Na 1.22 (Ti 1.19 Mn 0.60 Nb 0.21)}{ [A1,A2] Zn 1.03 (Ti 1.64 Nb 0.36)[Si 2 O 7 ] 2 }O 2 (O,OH) 2 (H 2 O) 4 for vigrishinite and {Na 1.14 (Ti 1.45 Mn 0.50 Nb 0.05)}{ [A1] Ca 0.77 [A2] Zn 0.13 (Ti 1.85 Nb 0.15)[Si 2 O 7 ] 2 }O 2 (OH,O) 2 (H 2 O) 4 and [B1] Zn 0.15 [B2] Ca 0.18 {Na 1.06 (Ti 1.32 Mn 0.60 Nb 0.08)}{ [A1] Zn 0.70 [A2] Ca 0.12 (Ti 1.74 Nb 0.26)[Si 2 O 7 ] 2 }O 2 (OH,O) 2 (H 2 O) 4 for the 5 and 24 hour Zn-exchanged forms of murmanite, respectively (braces give successively the contents of the octahedral O and heteropolyhedral H sheets). The triclinic (PÀ1) unit-cell parameters are respectively:

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Section: Crystal Structures: Description and Discussionmentioning

confidence: 99%

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Lykova¹,

Pekov²,

Zubkova³

et al. 2015

ejm

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“…1 amprophyllite (Sokolova and Hawthorne, 2008a), nacareniobsite (Ce) (Sokolova and Hawthorne, 2008b), lomonosovite and murmanite (Cámara et al, 2008), and jinshajiangite . Here, I describe the results for three minerals, delindeite, bornemanite and nabalamprophyllite 2O.…”

Section: Prediction Of Structural Arrangementsmentioning

confidence: 99%

Predictive crystal-chemical relations in Ti-silicates based on the TS block

Sokolova

2010

Geol. Ore Deposits

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In a group of minerals of reasonable complexity in which the structure topology is related but not identical, the general relation between structure topology and chemical composition is not known. This prob lem is of major significance. The structural hierarchy and stereochemistry are described for 27 titanium dis ilicate minerals that contain the TS (titanium silicate) block, a central trioctahedral (O) sheet and two adja cent (H) sheets of [5] and [6] coordinated polyhedra and (Si 2 O 7 ) groups and related delindeite. The TS block is characterized by a planar cell based on translation vectors, t 1 and t 2 , with t 1 ~ 5.5 and t 2 ~ 7 Å and t 1 ∧ t 2 close to 90°. The general formula of the TS block is (Si 2 O 7 ) 2 X 4 + n , where and = cations of the H and O sheets; M H = Ti (= Ti + Nb), Zr, Mn 2+ , Ca; M O = Ti, Zr, Mn 2+ , Ca, Na; A P and B P are cations at the peripheral (P) sites = Na, Ca, Ba; X = anions = O, OH, F; n = 0, 2, 4; the core part of the TS block is shown in bold and is invariant. Cations in each sheet of the TS block form a close packed layer and the three layers are cubic close packed. There are three topologically distinct TS blocks, depending on the type of linkage of two H sheets and the central O sheet. The H sheets of one TS block attach to the O sheet in the same manner. All structures consist of a TS block and an I (intermediate) block that comprises atoms between two TS blocks. Usually, the I block consists of alkali and alkaline earth cations, (H 2 O) groups and oxyanions (PO 4 ) 3-, (SO 4 ) 2-and (CO 3 ) 2-. These structures naturally fall into four groups, based on differences in topology and stereochemistry of the TS block. In Group I, Ti = 1 apfu Ti occurs in the O sheet, and (Si 2 O 7 ) groups link to a Na polyhedron of the O sheet (linkage 1). In Group II, Ti = 2 apfu, Ti occurs in the H sheet, and (Si 2 O 7 ) groups link to two M 2+ octahedra of the O sheet adjacent along t 2 (linkage 2). In Group III, Ti = 3 apfu, Ti occurs in the O and H sheets, and (Si 2 O 7 ) groups link to the Ti octahedron of the O sheet (linkage 1). In Group IV, Ti = 4 apfu (the maximum possible content of Ti in the TS block), Ti occurs in the O and H sheets, and (Si 2 O 7 ) groups link to two Ti octahedra of the O sheet adjacent along t 1 (linkage 3). The stability of the TS block is due to the ability of Ti (Nb) to have an extremely wide range in Ti (Nb) anion bond lengths, 1.68-2.30 Å, which allows the chemical composition of the TS block to vary widely. In crystal structures so far known, only one type of TS block occurs in a structure. The TS block propagates close packing of cations onto the I block. The gen eral structural principles and the relation between structure topology and chemical composition are described for the TS block minerals. These principles allow prediction of structural arrangements and possible chemi cal compositions, and testing whether or not all aspects of the structure and chemical formula of a mineral are correct. Here, I show how these principles work, and review recent...

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“…5a,b). (Cámara et al, 2008). There is disorder of Na and at the A P (2) site and H 2 O and at the W and X P A (2) sites, where Na at the A P (2) site (24% occupancy) and an H 2 O group at the X P A (2) site (24% occupancy) occur at short distances from an H 2 O group at the W site (76% occupancy), 1.65 and 0.61 Å, respectively (Table 6, Fig.…”

Section: Cation and Anion Sitesmentioning

confidence: 99%

From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na₂ZnTiNb₂(Si₂O₇)₂O₂(OH)₂(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

et al. 2017

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The 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.

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From structure topology to chemical composition. IX. Titanium silicates: revision of the crystal chemistry of lomonosovite and murmanite, Group-IV minerals

Cited by 32 publications

References 16 publications

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Predictive crystal-chemical relations in Ti-silicates based on the TS block

From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na₂ZnTiNb₂(Si₂O₇)₂O₂(OH)₂(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

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From structure topology to chemical composition. IX. Titanium silicates: revision of the crystal chemistry of lomonosovite and murmanite, Group-IV minerals

Cited by 32 publications

References 16 publications

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Crystal chemistry of cation-exchanged forms of epistolite-group minerals. Part II. Vigrishinite and Zn-exchanged murmanite

Predictive crystal-chemical relations in Ti-silicates based on the TS block

From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

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From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na₂ZnTiNb₂(Si₂O₇)₂O₂(OH)₂(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia