Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
Fluorapophyllite-(CS), CsCa4(Si8O20)F(H2O)8, a new apophyllite-group mineral from the Darai-pioz massif, Tien-Shan, northern Tajikistan. / Agakhanov, Atali A.; Pautov, Leonid A.; Kasatkin, Anatoly V.; Karpenko, Vladimir Y.U.; Sokolova, Elena; Day, Maxwell C.; Hawthorne, Frank C.; Muftakhov, Vyacheslav A.; Pekov, Igor V.; Cámara, Fernando; Britvin, Sergey N.
в: Canadian Mineralogist, Том 57, № 6, 2019.Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
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TY - JOUR
T1 - Fluorapophyllite-(CS), CsCa4(Si8O20)F(H2O)8, a new apophyllite-group mineral from the Darai-pioz massif, Tien-Shan, northern Tajikistan
AU - Agakhanov, Atali A.
AU - Pautov, Leonid A.
AU - Kasatkin, Anatoly V.
AU - Karpenko, Vladimir Y.U.
AU - Sokolova, Elena
AU - Day, Maxwell C.
AU - Hawthorne, Frank C.
AU - Muftakhov, Vyacheslav A.
AU - Pekov, Igor V.
AU - Cámara, Fernando
AU - Britvin, Sergey N.
PY - 2019
Y1 - 2019
N2 - Fluorapophyllite-(Cs) (IMA 2018-108a), ideally CsCa4(Si8O20)F(H2O)8, is an apophyllite-group mineral from the moraine of the Darai-Pioz glacier, Tien-Shan, Northern Tajikistan. Associated minerals are quartz, pectolite, baratovite, aegirine, leucosphenite, pyrochlore, neptunite, fluorapophyllite-(K), and reedmergnerite. Fluorapophyllite-(Cs) is a hydrothermal mineral. It is colorless and has a vitreous luster and a white streak. Cleavage is perfect; it is brittle and has a stepped fracture. Mohs hardness is 4.5-5. Dmeas. = 2.54(2) g/cm3, Dcalc. = 2.513 g/cm3. Fluorapophyllite-(Cs) is unixial (+) with refractive indices (λ = 589 nm) ω = 1.540(2), ε = 1.544(2). It is non-pleochroic. Chemical analysis by electron microprobe gave SiO2 48.78, Al2O3 0.05, CaO 22.69, Cs2O 10.71, K2O 1.13, Na2O 0.04, F 1.86, H2Ocalc. 14.61, -O=F2 -0.78, sum 99.09 wt.%; H2O was calculated from crystal-structure analysis. The empirical formula based on 29 (O + F) apfu, H2O = 8 pfu, is (Cs0.75K0.24)Σ0.99(Ca3.99Na0.01)Σ4(Si8.01Al0.01)Σ8.02O20.03F0.97(H2O)8, Z = 2. The simplified formula is (Cs,K)(Ca,Na)4(Si,Al)8 O20F(H2O)8. Fluorapophyllite-(Cs) is tetragonal, space group P4/mnc, a 9.060(6), c 15.741(11) Å, V 1292.10(19) Å3. The crystal structure has been refined to R1 = 4.31% based on 498 unique (Fo > 4σF) reflections. In the crystal structure of fluorapophyllite-(Cs), there is one [4]T site occupied solely by Si,,T-O. = 1.615 Å. SiO4 tetrahedra link to form a (Si8O20)8-sheet perpendicular to [001]. Between the Si-O sheets, there are two cation sites: A and B. The A site is coordinated by eight H2O groups [O(4) site], A-O(4) = 3.152(4) Å; the A site contains Cs0.75K0.24 0.01, ideally Cs apfu. The Cs-O bond length of 3.152 Å is definitely larger than the K-O bond length of 2.966-2.971 Å in fluorapophyllite-(K), KCa4(Si8O20)F(H2O)8. The [7]B site contains Ca3.99Na0.01, ideally Ca4 apfu;<B-φ> = 2.417 Å (φ = O, F, H2O). The Si-O sheets connect via A and B polyhedra and hydrogen bonding; two H atoms have been included in the refinement. Fluorapophyllite-(Cs) is isostructural with fluorapophyllite-(K). Fluorapophyllite-(Cs) is a Cs-analogue of fluorapophyllite-(K).
AB - Fluorapophyllite-(Cs) (IMA 2018-108a), ideally CsCa4(Si8O20)F(H2O)8, is an apophyllite-group mineral from the moraine of the Darai-Pioz glacier, Tien-Shan, Northern Tajikistan. Associated minerals are quartz, pectolite, baratovite, aegirine, leucosphenite, pyrochlore, neptunite, fluorapophyllite-(K), and reedmergnerite. Fluorapophyllite-(Cs) is a hydrothermal mineral. It is colorless and has a vitreous luster and a white streak. Cleavage is perfect; it is brittle and has a stepped fracture. Mohs hardness is 4.5-5. Dmeas. = 2.54(2) g/cm3, Dcalc. = 2.513 g/cm3. Fluorapophyllite-(Cs) is unixial (+) with refractive indices (λ = 589 nm) ω = 1.540(2), ε = 1.544(2). It is non-pleochroic. Chemical analysis by electron microprobe gave SiO2 48.78, Al2O3 0.05, CaO 22.69, Cs2O 10.71, K2O 1.13, Na2O 0.04, F 1.86, H2Ocalc. 14.61, -O=F2 -0.78, sum 99.09 wt.%; H2O was calculated from crystal-structure analysis. The empirical formula based on 29 (O + F) apfu, H2O = 8 pfu, is (Cs0.75K0.24)Σ0.99(Ca3.99Na0.01)Σ4(Si8.01Al0.01)Σ8.02O20.03F0.97(H2O)8, Z = 2. The simplified formula is (Cs,K)(Ca,Na)4(Si,Al)8 O20F(H2O)8. Fluorapophyllite-(Cs) is tetragonal, space group P4/mnc, a 9.060(6), c 15.741(11) Å, V 1292.10(19) Å3. The crystal structure has been refined to R1 = 4.31% based on 498 unique (Fo > 4σF) reflections. In the crystal structure of fluorapophyllite-(Cs), there is one [4]T site occupied solely by Si,,T-O. = 1.615 Å. SiO4 tetrahedra link to form a (Si8O20)8-sheet perpendicular to [001]. Between the Si-O sheets, there are two cation sites: A and B. The A site is coordinated by eight H2O groups [O(4) site], A-O(4) = 3.152(4) Å; the A site contains Cs0.75K0.24 0.01, ideally Cs apfu. The Cs-O bond length of 3.152 Å is definitely larger than the K-O bond length of 2.966-2.971 Å in fluorapophyllite-(K), KCa4(Si8O20)F(H2O)8. The [7]B site contains Ca3.99Na0.01, ideally Ca4 apfu;<B-φ> = 2.417 Å (φ = O, F, H2O). The Si-O sheets connect via A and B polyhedra and hydrogen bonding; two H atoms have been included in the refinement. Fluorapophyllite-(Cs) is isostructural with fluorapophyllite-(K). Fluorapophyllite-(Cs) is a Cs-analogue of fluorapophyllite-(K).
KW - Apophyllite group
KW - Crystal structure
KW - Darai-Pioz
KW - Electron microprobe analysis
KW - Fluorapophyllite-(Cs)
KW - New mineral
KW - Northern Tajikistan
KW - Tien-Shan
UR - http://www.scopus.com/inward/record.url?scp=85077206755&partnerID=8YFLogxK
U2 - 10.3749/CANMIN.1900038
DO - 10.3749/CANMIN.1900038
M3 - Article
AN - SCOPUS:85077206755
VL - 57
JO - Canadian Mineralogist
JF - Canadian Mineralogist
SN - 0008-4476
IS - 6
ER -
ID: 50635909