Research output: Contribution to journal › Article › peer-review
Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35, a new mineral from the Darai-Pioz alkaline massif, Tajikistan. / Agakhanov, Atali A.; Pautov, Leonid A.; Sokolova, Elena; Hawthorne, Frank C.; Karpenko, Vladimir Yu; Siidra, Oleg I.; Garanin, Viktor K.
In: Mineralogical Magazine, Vol. 81, No. 1, 01.02.2017, p. 135-141.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35, a new mineral from the Darai-Pioz alkaline massif, Tajikistan
AU - Agakhanov, Atali A.
AU - Pautov, Leonid A.
AU - Sokolova, Elena
AU - Hawthorne, Frank C.
AU - Karpenko, Vladimir Yu
AU - Siidra, Oleg I.
AU - Garanin, Viktor K.
PY - 2017/2/1
Y1 - 2017/2/1
N2 - Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35 is a new mineral from the Darai-Pioz alkaline massif, Tajikistan. Mendeleevite-(Nd) was found in a pectolite aggregate in silexites (quartz-rich rocks) which consist of fine to medium pectolite grains, quartz, aegirine and fluorite, with minor khvorovite, mendeleevite-(Ce), sokolovaite, hyalotekite, orlovite, kirchhoffite, pekovite, neptunite, zeravshanite, senkevichite, nordite-(e), alamosite, pyrochlore-group minerals and baratovite. Mendeleevite-(Nd) forms colourless cubic crystals 10-40 μm in size; it has a vitreous lustre and a Mohs hardness of 5-5.5; Dmeas. = 3.20(2) g/cm3, Dcalc. = 3.155 g/cm3. Mendeleevite-(Nd) is optically isotropic, with the refractive index n = 1.582(2). Mendeleevite-(Nd) is cubic, space group Pm3, a = 21.9106(4) Å; Z = 2. The six strongest reflections in the powder X-ray diffraction pattern are [d (Å), I (%), (h k l)] are: 11.01, 100, (0 0 2); 15.63, 55, (0 1 1); 3.47, 42, (2 0 6); 3.099, 42, (3 4 5); 2.192, 42, (0 0 10); 1.819, 41, (3 6 10). Chemical analysis by electron microprobe gave SiO2 42.30, Ce2O3 10.12, La2O3 3.60, Nd2O3 16.19, Pr2O3 2.79, Sm2O3 4.19, Gd2O3 1.69, Eu2O3 0.47, SrO 2.99, CaO 2.20, Cs2O 8.50, K2O 0.85, H2O 3.85, F 1.25, -O = F2 -0.53, sum 100.46 wt.%, with H2O calculated by analogy with mendeleevite-(Ce). The empirical formula based on 210 (O + F) apfu, with F + OH + H2O = 35 pfu, is Cs6(□4.20K1.80)Σ6{[(Nd9.57Ce6.13Sm2.39La2.20Pr1.68Gd0.93Eu0.27)Σ23.17(Ca3.90Sr2.87)Σ6.77]Σ29.94□0.06}Σf30(Si70O175)(OH, H2O,F)35 and Cs6(REE23Ca7)(Si70O175)(OH,F)19(H2O)16, respectively. The compatibility index (from measured density) = -0.039 (excellent). Mendeleevite-(Nd) is a Nd analogue of mendeleevite-(Ce), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca,□)30(Si70O175)(H2O,OH,F,□)35. Both minerals are named after Dmitri Mendeleev (1834-1907), the great Russian chemist, author of the periodic table of chemical elements, who has had a significant impact on the development of natural sciences and industry, both in Russia and around the world.
AB - Mendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35 is a new mineral from the Darai-Pioz alkaline massif, Tajikistan. Mendeleevite-(Nd) was found in a pectolite aggregate in silexites (quartz-rich rocks) which consist of fine to medium pectolite grains, quartz, aegirine and fluorite, with minor khvorovite, mendeleevite-(Ce), sokolovaite, hyalotekite, orlovite, kirchhoffite, pekovite, neptunite, zeravshanite, senkevichite, nordite-(e), alamosite, pyrochlore-group minerals and baratovite. Mendeleevite-(Nd) forms colourless cubic crystals 10-40 μm in size; it has a vitreous lustre and a Mohs hardness of 5-5.5; Dmeas. = 3.20(2) g/cm3, Dcalc. = 3.155 g/cm3. Mendeleevite-(Nd) is optically isotropic, with the refractive index n = 1.582(2). Mendeleevite-(Nd) is cubic, space group Pm3, a = 21.9106(4) Å; Z = 2. The six strongest reflections in the powder X-ray diffraction pattern are [d (Å), I (%), (h k l)] are: 11.01, 100, (0 0 2); 15.63, 55, (0 1 1); 3.47, 42, (2 0 6); 3.099, 42, (3 4 5); 2.192, 42, (0 0 10); 1.819, 41, (3 6 10). Chemical analysis by electron microprobe gave SiO2 42.30, Ce2O3 10.12, La2O3 3.60, Nd2O3 16.19, Pr2O3 2.79, Sm2O3 4.19, Gd2O3 1.69, Eu2O3 0.47, SrO 2.99, CaO 2.20, Cs2O 8.50, K2O 0.85, H2O 3.85, F 1.25, -O = F2 -0.53, sum 100.46 wt.%, with H2O calculated by analogy with mendeleevite-(Ce). The empirical formula based on 210 (O + F) apfu, with F + OH + H2O = 35 pfu, is Cs6(□4.20K1.80)Σ6{[(Nd9.57Ce6.13Sm2.39La2.20Pr1.68Gd0.93Eu0.27)Σ23.17(Ca3.90Sr2.87)Σ6.77]Σ29.94□0.06}Σf30(Si70O175)(OH, H2O,F)35 and Cs6(REE23Ca7)(Si70O175)(OH,F)19(H2O)16, respectively. The compatibility index (from measured density) = -0.039 (excellent). Mendeleevite-(Nd) is a Nd analogue of mendeleevite-(Ce), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca,□)30(Si70O175)(H2O,OH,F,□)35. Both minerals are named after Dmitri Mendeleev (1834-1907), the great Russian chemist, author of the periodic table of chemical elements, who has had a significant impact on the development of natural sciences and industry, both in Russia and around the world.
KW - alkaline rocks
KW - Darai-Pioz massif
KW - electron microprobe analysis
KW - mendeleevite-(Ce)
KW - mendeleevite-(Nd)
KW - new mineral species
KW - Tajikistan
UR - http://www.scopus.com/inward/record.url?scp=85014558634&partnerID=8YFLogxK
U2 - 10.1180/minmag.2016.080.0763
DO - 10.1180/minmag.2016.080.0763
M3 - Article
AN - SCOPUS:85014558634
VL - 81
SP - 135
EP - 141
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 1
ER -
ID: 9144239