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

Sokolova, Elena

doi:10.1134/s1075701510050065

Cited by 5 publications

(2 citation statements)

References 27 publications

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“…Ferraris (1997) introduced the notation HÀOÀH (by analogy with TÀOÀT) to denote two heteropolyhedral (H) sheets intercalating an octahedral (O) sheet. Sokolova (2006Sokolova ( , 2010 divided the TS-block minerals into four groups based on the different topology and stereochemistry of the TS block, and showed that these groups have different contents of (Ti + Nb). The basic unit of this series of structures is the HÀOÀH block (Fig.…”

Section: Hàoàh Structures: Ti-silicatesmentioning

confidence: 99%

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

Hawthorne¹

2012

Mineral. mag.

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Aspects of the bond topology and chemical composition of a mineral may be incorporated into a general formula by writing the local topological details of each cation and anion, along with their chemical identity, as a general expression called a structure-generating function. Here, this procedure is described for polysomatic TÀOÀT and HÀOÀH structures. We may write tetrahedrally coordinated cations and their associated anions as {T 2n Y m }. For {T 2n Y m } to be a chain or ribbon, 5n < m 4 6n, and we may write m as 5n + N, where N is an integer. Within the {T 2n Y (5n+N) } unit, we may recognize three types of anion vertices: (1) bridging anions, Y br , that are bonded to two T cations; (2) apical anions, Y ap , that are involved in linkage to other cations out of the plane of the bridging anions; and (3) linking anions, Y l , that link to non-T cations in the plane of the bridging anions. We may incorporate the connectivity of the cations in our algebraic representation of the chain as follows: {T 2n Y br a Y ap b Y l c } where a + b + c = 5n + N. The apical anions of the T-or H-sheets provide some anions of the layer of octahedra. We may use the handshaking di-lemma of graph theory to examine the interaction between the two types of layers, and write a Structure-Generating Function, S (N;n) , that gives both the stoichiometry and aspects of the bond topology of the structures.Where N = 1, the T-sheet consists of ribbons of the form {T 2n Y (5n+1) } = {T 2n Y br (3nÀ1) Y ap 2n Y l 2 }. Each TÀY br ÀT linkage spans an octahedron, and hence there are (3n À 1) octahedrally coordinated cations between opposing {T 2n Y br (3nÀ1) Y ap 2n Y l 2 } ribbons. There are an additional (n À 1) vertices, C, required to complete the coordination of the M cations on one side of the O-sheet, and we may write the structuregenerating function for biopyriboles as follows:5n+1) } 2 ]. Where N = 2, the general form of the T-ribbon is {T 2n Y (5n+2) }, a component of the H-sheet in the polysomatic HÀOÀH minerals in which the T-ribbons are linked laterally by [5]-or [6]-coordinated high-valence cations, D, which have the coordination (DY l 4 F ap F t ), where F t may or may not be present depending on the coordination number, [6] or [5], of the D cation. The general formula for an H, where F t (written after the T-sheet) occurs on the outside of the H-sheet and may be involved in linkage between adjacent HÀOÀH blocks. The H-sheet links via its apical anions to the O-sheet, giving the general formula of an HÀOÀH block as [M (3n+1) (DF ap C n {T 2n Y (5n+2) }F t 0À1 ) 2 ]. These HÀOÀH blocks may link directly or indirectly through the F t anions of the (DY l 4 F a p F t ) octahedra, giving S ( 2 ; n ) =. Combining the expressions for the structuregenerating functions gives a single function for TÀOÀT and HÀOÀH structures:* This expression also generates mixed-ribbon polysomatic structures. Thus S (1;2+3) gives the chemical composition and structure of the mixed-chain pyribole chesterite, and S (2;1+4) gives the chemical composition and s...

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Section: Hàoàh Structures: Ti-silicatesmentioning

confidence: 99%

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

Hawthorne¹

2012

Mineral. mag.

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“…The TS block consists of HOH sheets (H = heteropolyhedral and O = octahedral) and 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 seidozerite-supergroup minerals are divided into four groups based on the content of Ti (+ Nb + Zr + Fe 3+ + Mg + Mn), topology, chemical composition and stereochemistry of the TS block (Sokolova, 2006, 2010; Sokolova and Cámara, 2013). In the rinkite, bafertisite, lamprophyllite and murmanite groups, Ti = 1, 2, 3 and 4 apfu (atoms per formula unit).…”

Section: Introductionmentioning

confidence: 99%

From structure topology to chemical composition. XXIV. Revision of the crystal structure and chemical formula of vigrishinite, NaZnTi₄(Si₂O₇)₂O₃(OH)(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

Sokolova

Hawthorne

2018

Mineral. mag.

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The crystal structure of vigrishinite, ideally NaZnTi4(Si2O7)2O3(OH)(H2O)4, a murmanite-group mineral of the seidozerite supergroup from the type locality, Mt. Malyi Punkaruaiv, Lovozero alkaline massif, Kola Peninsula, Russia, was refined in space group C$\bar 1$, a = 10.530(2), b = 13.833(3), c = 11.659(2) Å, α = 94.34(3), β = 98.30(3), γ = 89.80(3)°, V = 1675.5(2.1) Å3 and R1 = 12.52%. Based on electron-microprobe analysis, the empirical formula calculated on 22 (O + F), with two constraints derived from structure refinement, OH + F = 1.96 pfu and H2O = 3.44 pfu, is: (Na0.67Zn0.21Ca0.05□1.07)Σ2 (Zn0.86□1.14)Σ2(Zn0.14□0.36)Σ0.5(Ti2.60Nb0.62Mn0.30${\rm Fe}_{{\rm 0}{\rm. 23}}^{{\rm 2 +}} $Mg0.10Zr0.06Zn0.05Al0.03Ta0.01)Σ4(Si4.02O14) [O2.60(OH)1.21F0.19]Σ4[(H2O)3.44(OH)0.56]Σ4{Zn0.24P0.03K0.03Ba0.02} with Z = 4. It seems unlikely that constituents in the {} belong to vigrishinite itself. The crystal structure of vigrishinite is an array of TS blocks (Titanium Silicate) connected via hydrogen bonds. The TS block consists of HOH sheets (H = heteropolyhedral and O = octahedral) parallel to (001). In the O sheet, the Ti-dominant MO(1,2) sites, Na-dominant MO(3) and □-dominant MO(4) sites give ideally Na□Ti2 pfu. In the H sheet, the Ti-dominant MH(1,2) sites, Zn-dominant AP(1) and vacant AP(2) sites give ideally Zn□Ti2 pfu. The MH and AP(1) polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula of vigrishinite of the form ${\rm A}_{\rm 2}^{P} {\rm M}_{\rm 2}^{\rm H} {\rm M}_{\rm 4}^{\rm O} $(Si2O7)2(${\rm X}_{\rm M}^{\rm O} $)2(${\rm X}_{\rm A}^{\rm O} $)2(${\rm X}_{{\rm M,A}}^{P} $)4 is Zn□Ti2Na□Ti2(Si2O7)2O2O(OH)(H2O)4. Vigrishinite is a Zn-bearing, Na-poor and OH-rich analogue of murmanite, ideally Na2Ti2Na2Ti2(Si2O7)2O2O2(H2O)4. Murmanite and vigrishinite are related by the following substitution: H(${\rm Na}_{\rm 2}^{\rm +} $)mur + O(Na+)mur + O(O2–)mur ↔ H(Zn2+)vig + H(□)vig + O(□)vig + O[(OH)–]vig. The doubling of the t1 and t2 translations of vigrishinite compared to those of murmanite is due to the order of Zn and □ in the H sheet and Na and □ in the O sheet of vigrishinite.

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From structure topology to chemical composition. XXVII. Revision of the crystal chemistry of the perraultite-type minerals of the seidozerite supergroup: Jinshajiangite, surkhobite, and bobshannonite

Sokolova

Hawthorne

Cámara

et al. 2020

The Canadian Mineralogist

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The crystal structures of the three perraultite-type minerals (bafertisite group, seidozerite supergroup)—jinshajiangite from Norra Kärr, Sweden, ideally NaBaFe2+4Ti2(Si2O7)2O2(OH)2F, Z = 4; surkhobite (holotype) from the Darai-Pioz massif, Tajikistan, ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4; and bobshannonite (holotype) from Mont Saint-Hilaire, Canada, ideally Na2KBa(Mn7Na)Nb4(Si2O7)4O4(OH)4O2, Z = 2—were refined in space group C to R1 = 2.73, 2.85, and 2.02% on the basis of 2746, 2657, and 4963 unique reflections [Fo > 4σFo], respectively. Refinement was done using data from twinned crystals (jinshajiangite: three twin components; surkhobite and bobshannonite: two twin components). The parameters of a C-centered triclinic unit cell are as follows: jinshajiangite: a = 10.720(5), b = 13.823(7), c = 11.044(6) Å, α = 108.222(6), β = 99.28(1), γ = 89.989(6)°, V = 1532.0(2.2) Å3; surkhobite: a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; and bobshannonite: a = 10.831(7), b = 13.903(9), c = 11.149(8) Å, α = 108.145(6), β = 99.215(9), γ = 90.007(7)°, V = 1572.6(3.2) Å3. New electron microprobe data are reported for the holotype surkhobite and new IR data for jinshajiangite. In the perraultite-type structure (structure type B1BG, B – basic, BG – bafertisite group), there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Fe2+4apfu (jinshajiangite), Mn4apfu (surkhobite), and (Mn7Na) (bobshannonite). There is no order of Fe2+ and Mn in the O sheet. In the H sheet, the ideal composition of the two [6]MH sites is Ti2apfu (jinshajiangite, surkhobite) and Nb4apfu (bobshannonite). The four [4]Si sites are occupied solely by Si. The MH octahedra and Si2O7 groups constitute the H sheet. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. In the I block of jinshajiangite and surkhobite, the AP(1) site is occupied by Ba and the AP(2) site by K > Ba; the ideal composition of the two AP(1,2) sites is Ba apfu. In the I block of bobshannonite, Ba and K are ordered at the AP(1) and AP(2) sites, Ba:K ∼ 1:1 , ideally BaK apfu. The two BP(1,2) sites are each occupied by Na > Ca, ideally Na apfu (jinshajiangite, surkhobite) and solely by Na, ideally Na2apfu (bobshannonite). There is no order of Na and Ca at the BP(1,2) sites in jinshajiangite and surkhobite [currently defined as a Ca-ordered analogue of perraultite, ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4]. The ideal formulae of surkhobite, KBa3Ca2Na2Mn16Ti8(Si2O7)8O8(OH)4(F,O,OH)8 (current IMA formula) and of bobshannonite, Na2KBa(Mn,Na)8(Nb,Ti)4(Si2O7)4O4(OH)4(O,F)2 (current IMA formula) have been revised as follows: NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4 (surkhobite) and Na2KBa(Mn7Na)Nb4(Si2O7)4O4(OH)4O2, Z = 2 (bobshannonite). The revised ideal formula of surkhobite is identical to the ideal formula of perraultite and hence surkhobite should be discredited.

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

Cited by 5 publications

References 27 publications

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

From structure topology to chemical composition. XXIV. Revision of the crystal structure and chemical formula of vigrishinite, NaZnTi₄(Si₂O₇)₂O₃(OH)(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

From structure topology to chemical composition. XXVII. Revision of the crystal chemistry of the perraultite-type minerals of the seidozerite supergroup: Jinshajiangite, surkhobite, and bobshannonite

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

Cited by 5 publications

References 27 publications

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

Bond topology and structure-generating functions: graph-theoretic prediction of chemical composition and structure in polysomatic T–O–T (biopyribole) and H–O–H structures

From structure topology to chemical composition. XXIV. Revision of the crystal structure and chemical formula of vigrishinite, NaZnTi4(Si2O7)2O3(OH)(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia

From structure topology to chemical composition. XXVII. Revision of the crystal chemistry of the perraultite-type minerals of the seidozerite supergroup: Jinshajiangite, surkhobite, and bobshannonite

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From structure topology to chemical composition. XXIV. Revision of the crystal structure and chemical formula of vigrishinite, NaZnTi₄(Si₂O₇)₂O₃(OH)(H₂O)₄, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia