The crystal structure of jinshajiangite, ideally BaNaTi(2)Fe(4)(2+) (Si(2)O(7))(2) O(2)(OH)(2)F, a 10.6785(8), b 13.786(1), c 20.700(2) angstrom, beta 94.937(1)degrees, V 3035.93(6) angstrom(3), sp. gr. C2/m, Z = 8, D(calc). 3.767 g/cm(3), from Norra Karr, Tonkoping province, Sweden, has been refined to R(1) 5.69% on the basis of 3193 unique reflections (F(O) > 4 sigma F). Electron microprobe analysis gave (wt%): SiO(2) 27.56, Nb(2)O(5) 0.12, TiO(2) 18.36, ZrO(2) 0.51, FeO 23.42, Fe(2)O(3) 2.89 [the Fe(3+)/Fe(tot) ratio of 0.10(9) was determined by Mossbauer spectroscopy.], MnO 5.13, MgO 0.44, CaO 2.52, BaO 10.24, K(2)O 1.95, Na(2)O 2.27, F 2.33, H(2)O 2.00 (calc. from structure refinement: OH + F = 3 apfu), O = F - 0.98, total 98.76. The empirical formula is (Ba(0.58)K(0.36))(Sigma 0.94)(Na(0.57)Ca(0.39))(Sigma 0.96) (Fe(2.84)(2+)Mn(0.63)Fe(0.32)(3+)Mg(0.10)Zr(0.04)Na(0.07))(Sigma 4.00)(Ti(2.00)Nb(0.01))(Sigma 2.01) (Si(2)O(7))(2)O(2.12)(OH)(1.93)F(1.07), calculated on the basis of 4 Si apfu. The crystal structure of jinshajiangite can be described as a combination of a TS block and an I block. The TS (titanium silicate) block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is a component of 27 Ti-disilicate minerals. In the O sheet, there are five [6]-coordinated M(O) sites occupied mainly by Fe(2+) and Mn(2+), with minor Fe(3+), Mg, Zr and Na with < M(O)-O > = 2.175 angstrom. Five M(O) sites give ideally Fe(4)(2+) pfu. In the H sheet, there are three [6]-coordinated M(H) sites occupied solely by Ti (Ti = 2 apfu), with < M(H)-O > = 1.953 angstrom, and four [4]-coordinated Si sites occupied solely by Si, with < Si-O > = 1.619 angstrom. The M(H) octahedra and (Si(2)O(7)) groups constitute the H sheet. Linkage of H and O sheets via common vertices of M(H) octahedra and (Si(2)O(7)) groups with M(O)(1-5) octahedra results in a TS block. The topology of the TS block is as in Group II of the Ti disilicates (Ti = 2 apfu). There are six interstitial sites, three [9-10]-coordinated Ba-dominant A(P) sites with < A(P)-O > = 2.98 angstrom and three [10]-coordinated Na-dominant B(P) sites with < B(P)-O > = 2.600 angstrom. The total content of three A(P) sites sums to similar to 1 apfu = Ba(0.58) K(0.36) or ideally 1 Ba pfu. The total content of the three B(P) sites is Na(0.57)Ca(0.39) or ideally 1 Na pfu. Along c, the TS blocks link via common vertices of M(H) octahedra (as in astrophyllite-group minerals) and A(P) and B(P) sites which constitute the I block. Jinshajiangite is an Fe(2+) analogue of perraultite, ideally BaNaTi(2)Mn(4)(2+) (Si(2)O(7))(2)O(2)(OH)(2)F, and its crystal structure is topologically identical to that of perraultite.
From structure topology to chemical composition. VII. Titanium silicates: the crystal structure and crystal chemistry of jinshajiangite
CAMARA ARTIGAS, Fernando;
2009-01-01
Abstract
The crystal structure of jinshajiangite, ideally BaNaTi(2)Fe(4)(2+) (Si(2)O(7))(2) O(2)(OH)(2)F, a 10.6785(8), b 13.786(1), c 20.700(2) angstrom, beta 94.937(1)degrees, V 3035.93(6) angstrom(3), sp. gr. C2/m, Z = 8, D(calc). 3.767 g/cm(3), from Norra Karr, Tonkoping province, Sweden, has been refined to R(1) 5.69% on the basis of 3193 unique reflections (F(O) > 4 sigma F). Electron microprobe analysis gave (wt%): SiO(2) 27.56, Nb(2)O(5) 0.12, TiO(2) 18.36, ZrO(2) 0.51, FeO 23.42, Fe(2)O(3) 2.89 [the Fe(3+)/Fe(tot) ratio of 0.10(9) was determined by Mossbauer spectroscopy.], MnO 5.13, MgO 0.44, CaO 2.52, BaO 10.24, K(2)O 1.95, Na(2)O 2.27, F 2.33, H(2)O 2.00 (calc. from structure refinement: OH + F = 3 apfu), O = F - 0.98, total 98.76. The empirical formula is (Ba(0.58)K(0.36))(Sigma 0.94)(Na(0.57)Ca(0.39))(Sigma 0.96) (Fe(2.84)(2+)Mn(0.63)Fe(0.32)(3+)Mg(0.10)Zr(0.04)Na(0.07))(Sigma 4.00)(Ti(2.00)Nb(0.01))(Sigma 2.01) (Si(2)O(7))(2)O(2.12)(OH)(1.93)F(1.07), calculated on the basis of 4 Si apfu. The crystal structure of jinshajiangite can be described as a combination of a TS block and an I block. The TS (titanium silicate) block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is a component of 27 Ti-disilicate minerals. In the O sheet, there are five [6]-coordinated M(O) sites occupied mainly by Fe(2+) and Mn(2+), with minor Fe(3+), Mg, Zr and Na with < M(O)-O > = 2.175 angstrom. Five M(O) sites give ideally Fe(4)(2+) pfu. In the H sheet, there are three [6]-coordinated M(H) sites occupied solely by Ti (Ti = 2 apfu), with < M(H)-O > = 1.953 angstrom, and four [4]-coordinated Si sites occupied solely by Si, with < Si-O > = 1.619 angstrom. The M(H) octahedra and (Si(2)O(7)) groups constitute the H sheet. Linkage of H and O sheets via common vertices of M(H) octahedra and (Si(2)O(7)) groups with M(O)(1-5) octahedra results in a TS block. The topology of the TS block is as in Group II of the Ti disilicates (Ti = 2 apfu). There are six interstitial sites, three [9-10]-coordinated Ba-dominant A(P) sites with < A(P)-O > = 2.98 angstrom and three [10]-coordinated Na-dominant B(P) sites with < B(P)-O > = 2.600 angstrom. The total content of three A(P) sites sums to similar to 1 apfu = Ba(0.58) K(0.36) or ideally 1 Ba pfu. The total content of the three B(P) sites is Na(0.57)Ca(0.39) or ideally 1 Na pfu. Along c, the TS blocks link via common vertices of M(H) octahedra (as in astrophyllite-group minerals) and A(P) and B(P) sites which constitute the I block. Jinshajiangite is an Fe(2+) analogue of perraultite, ideally BaNaTi(2)Mn(4)(2+) (Si(2)O(7))(2)O(2)(OH)(2)F, and its crystal structure is topologically identical to that of perraultite.
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