MALEEVITE, BaB2Si2O8, AND PEKOVITE, SrB2Si2O8, NEW MINERAL SPECIES FROM THE DARA-I-PIOZ ALKALINE MASSIF, NORTHERN TAJIKISTAN: DESCRIPTION AND CRYSTAL STRUCTURE

Pautov, Leonid A.; Agakhanov, Atali A.; Sokolova, Elena; Hawthorne, Frank C.

doi:10.2113/gscanmin.42.1.107

Cited by 30 publications

(18 citation statements)

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“…8 The XRD patterns of the slurries for the specimens SBSB-1 and SBSB-2 Fig. 9 The XRD patterns of the specimens SBSB-3 and SBSB-5 content and is closed the composition of a nature mineral, pekovite [16], obtain a good sintering behavior and a high Q 9 f value. As well known, SrB 2 Si 2 O 8 is an alkaline borosilicate mineral with a Pekovite (Danburite) crystal structure.…”

Section: Resultsmentioning

confidence: 98%

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Chen

Zhu

Sun

et al. 2013

J Mater Sci: Mater Electron

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In this paper, the sintering behavior of the SrB 2 Si 2 O 8 ceramics based on the SrO-B 2 O 3 -SiO 2 composition has been investigated. The influence of the BaO addition to the SrO-B 2 O 3 -SiO 2 ceramics on the sintering behavior has been also examined. It shows that, due to the low-meting characteristics of the SrO-B 2 O 3 binary composition, the SrB 2 Si 2 O 8 ceramics with peculiar dielectric properties can easily prepared by the introduction of SiO 2 to the SrO-B 2 O 3 binary compositions at a sintering temperature of 950°C. Additionally, the introduction of BaO to SrO-B 2 O 3 -SiO 2 ceramics has an obvious effect on the sintering behavior of the SrB 2 Si 2 O 8 ceramics. Also, the dielectric properties of the SrB 2 Si 2 O 8 ceramics are correlative to the phase compositions and the microstructures.

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Section: Resultsmentioning

confidence: 98%

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Chen

Zhu

Sun

et al. 2013

J Mater Sci: Mater Electron

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“…Alkali-earth representatives of this [28], and maleevite BaB 2 Si 2 O 6 [28] minerals. Three-dimensional frameworks are formed from 4-, 6-, and 8-membered rings.…”

Section: Crystal Structures Of Borate-silicates Of Alkali and Alkali-mentioning

confidence: 94%

“…The most common are 6-membered rings, they are found in the structures of all borosilicates of the group under consideration. The next most common are 4-membered rings ( [11]; the frameworks of monoclinic [16] and hexagonal [17] modifications of NaBSiO 4 are identical to the tridymite framework; MBSi 3 O 8 compounds (M = Na [18], K [19]) are isostructural with feldspar; poudretteite NaKB 3 Si 12 O 30 [20] is similar to osumilite; MBSi 2 O 6 (M = K [21,22], Rb [22,23], Cs [24]) belongs to the analcime (ANA) type with topologically identical framework (4 different structural types); [26], Ca [27], Sr [28], Ba [28]) are similar to paracelsian BaAl 2 Si 2 O 8 .…”

Section: Crystal Structures Of Borate-silicates Of Alkali and Alkali-mentioning

confidence: 99%

Crystallography and high-temperature crystal chemistry of anhydrous borosilicates of alkali and alkali-earth metals

2014

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UDC 548.3The crystal structures and thermal behavior of anhydrous borate-silicates of alkali and alkali-earth metals are briefly overviewed. In silicoborates (B/Si > 1), the boron atoms occur in triangle and tetrahedral coordination, as in borates; in two of three known silicoborates, the unique layered and chained polyanions are found. The known borosilicates (B/Si ≤ 1) have a framework structure formed from tetrahedrally coordinated atoms of boron and silicon; some borosilicates belong to the known structural types of aluminosilicates, while the others are only structurally similar to them and silica modifications, whereas their tetrahedral frameworks are topologically identical to that of aluminosilicates and SiO 2 . The exception are borosilicates Li 4 B 4 Si 8 O 24 and lisitsynite KBSi 2 O 6 , having the original frameworks. In line with the similarity of chemical composition and commonality of crystal structure, thermal behavior of borosilicates appears to be similar to that of aluminosilicates and silicates, however, borosilicates have considerably lower temperatures of formation, polymorphic transformations, and melting.

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“…A characteristic feature of the geochemistry of the Darai-Pioz massif is the boron enrichment (Dusmatov et al, 1972), expressed in the widespread occurrence of many borosilicates. Some of them have been described as new mineral species: calcybeborosilite-(Y) (Semenov et al, 1963;Rastsvetaeva et al, 1996;Pekov et al, 2000), tienshanite (Dusmatov et al, 1967a;Malinovskii et al, 1977;Cooper et al, 1998), tadzhikite-(Ce) (Efimov et al, 1970;Chernitsova et al, 1982;Hawthorne et al, 1998), kapitsaite-(Y) Sokolova et al, 2000), pekovite and maleevite (Pautov et al, 2004), byzantievite (Sokolova et al, 2010;Pautov et al, 2011), kirchhoffite (Agakhanov et al, 2012), laptevite- (Agakhanov et al, 2013;Uvarova et al, 2013). In some pegmatites, reedmergnerite, a boron analogue of albite, is a rock-forming mineral (Dusmatov et al, 1967b).…”

Section: Occurrencementioning

confidence: 99%

Khvorovite, Pb²⁺₄Ca₂[Si₈B₂(SiB)O₂₈]F, a new hyalotekite-group mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure

et al. 2015

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Khvorovite, ideally Pb42+Ca2[Si8B2(SiB)O28]F, is a new borosilicate mineral of the hyalotekite group from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, Tajikistan. Khvorovite was found in a pectolite aggregate in silexites (quartz-rich rocks). The pectolite aggregate consists mainly of pectolite, quartz and fluorite, with minor aegirine, polylithionite, turkestanite and baratovite; accessory minerals are calcite, pyrochlore-group minerals, reedmergnerite, stillwellite-(Ce), pekovite, zeravshanite, senkevichite, sokolovaite, mendeleevite-(Ce), alamosite, orlovite, leucosphenite and several unknown Cs-silicates. Khvorovite occurs as irregular grains, rarely with square or rectangular sections up to 150 μm, and grain aggregates up to 0.5 mm. Khvorovite is colourless, rarely white, transparent with a white streak, has a vitreous lustre and does not fluoresce under ultraviolet light. Cleavage and parting were not observed. Mohs hardness is 5–5.5, and khvorovite is brittle with an uneven fracture. The measured and calculated densities are 3.96(2) and 3.968 g/cm3, respectively. Khvorovite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.659(3), βcalc. = 1.671(2), γ = 1.676(3); 2Vmeas. = 64(3)°, medium dispersion: r < v. Khvorovite is triclinic, space group I1¯, a = 11.354(2), b = 10.960(2), c = 10.271(2) Å, α = 90.32(3), β = 90.00(3), γ = 90.00(3)°, V = 1278(1) Å3, Z = 2. The six strongest lines in the powder X-ray diffraction pattern [d (Å), I, (hkl)] are: 7.86, 100, (110); 7.65, 90, (101); 7.55, 90, (011); 3.81, 90, (202); 3.55, 90, (301); 2.934, 90, (312, 312). Chemical analysis by electron microprobe gave SiO2 36.98, B2O3 6.01, Y2O3 0.26, PbO 40.08, BaO 6.18, SrO 0.43, CaO 6.77, K2O 1.72, Na2O 0.41, F 0.88, O=F –0.37, sum 99.35 wt.%. The empirical formula based on 29 (O+F) a.p.f.u. is (Pb2.762+Ba0.62K0.56Na0.16)Σ4.10(Ca1.86Sr0.06Y0.04Na0.04)Σ2[Si8B2(Si1.46B0.65)Σ2.11O28](F0.71O0.29), Z = 2 , and the simplified formula is (Pb2+, Ba, K)4Ca2[Si8B2(Si,B)2O28]F. The crystal structure of khvorovite was refined to R1 = 2.89% based on 3680 observed reflections collected on a four-circle diffractometer with MoKα radiation. In the crystal structure of khvorovite, there are four [4]-coordinated Si sites occupied solely by Si with <Si–O>= 1.617 Å. The [4]-coordinated B site is occupied solely by B, with <B–O> = 1.478 Å. The [4]-coordinated T site is occupied by Si and B (Si1.46B0.54), with <T–O> = 1.605 Å; it ideally gives (SiB) a.p.f.u. The Si, B and T tetrahedra form an interrupted framework of ideal composition [Si8B2(SiB)O28]11–. The interstitial cations are Pb2+, Ba and K (minor Na) [A(11–22) sites] and Ca [M site]. The two A sites are each split into two subsites ∼0.5 Å apart and occupied by Pb2+ and Ba + K. The [8]-coordinated M site is occupied mainly by Ca, with minor Sr, Y and Na. Khvorovite is a Pb2+ analogue of hyalotekite, (Ba,Pb2+,K)4(Ca,Y)2[Si8(B,Be)2(Si,B)2O28]F and a Pb2+-, Ca-analogue of kapitsaite-(Y), (Ba,K)4(Y,Ca)2[Si8B2(B,Si)2O28]F. It is named after Pavel V. Khvorov (b. 1965), a Russian mineralogist, to honour his contribution to the study of the mineralogy of the Darai-Pioz massif.

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MALEEVITE, BaB2Si2O8, AND PEKOVITE, SrB2Si2O8, NEW MINERAL SPECIES FROM THE DARA-I-PIOZ ALKALINE MASSIF, NORTHERN TAJIKISTAN: DESCRIPTION AND CRYSTAL STRUCTURE

Cited by 30 publications

References 10 publications

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Crystallography and high-temperature crystal chemistry of anhydrous borosilicates of alkali and alkali-earth metals

Khvorovite, Pb²⁺₄Ca₂[Si₈B₂(SiB)O₂₈]F, a new hyalotekite-group mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure

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MALEEVITE, BaB2Si2O8, AND PEKOVITE, SrB2Si2O8, NEW MINERAL SPECIES FROM THE DARA-I-PIOZ ALKALINE MASSIF, NORTHERN TAJIKISTAN: DESCRIPTION AND CRYSTAL STRUCTURE

Cited by 30 publications

References 10 publications

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

Crystallography and high-temperature crystal chemistry of anhydrous borosilicates of alkali and alkali-earth metals

Khvorovite, Pb2+4Ca2[Si8B2(SiB)O28]F, a new hyalotekite-group mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure

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Khvorovite, Pb²⁺₄Ca₂[Si₈B₂(SiB)O₂₈]F, a new hyalotekite-group mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure