( by R. 01denbourg Verlag, MUnchen 1996 The crystal structure of christelite Zn3Cu2 (SO 4)2(OH)6 . 4 H20 G. Adiwidjaja, K. Friese, K.-H. Klaska* and J. Schluter Univcrsitiit Hamburg, Mineralogisch-Pctrographischcs Institut, Grindclallce 48, 0-20146 Hamburg, Germany Dedicated to Professor 0110 H. Jarclu})l' 011the occasioll of" his 65th hirthday Received November 11, 1995; accepted March L 1996 Natural single crystal / Zn-Cu minerals / Christelite tion rules were observed leading to the possible space groups PI or PI. The lattice parameters were determined Abstract. The crystal structure of christe]ite Zn3Cu2 by least-squares fitting of the e values of 25 reflections . (S04)2(OH)6 4 H20 (space group pI; lattice param- measured with a CAD4 single crystal diffractometer eters a = 5.4143(8) A, h = 6.336(1) A, c = 10.470(3) A, using AgK, radiation; their values are a = 5.4143(8) A, x = 94.32(3)", f3 = 90.06(2)', I' = 90.27(2)') was solved h = 6.336( I) A, c = 10.470(3) A, x = 94.32(3)', f3 = using direct methods and difference Fourier-syntheses. 90.06(2), = 90.27(2)'. The structure was refined to a final R(F)-va]ue of 0.033. Intensity" data were collected on the same diffracto- The structure contains distorted [(Zn, CU)06] octa- meter also using AgK, radiation with an (JJ - 20 scan in hedra which are connected as to form sheets of composi- the O-range 2-23'. The individual (JJ-scan angle for a tion ; [(Cu,Znh(OHhOr . These sheets are similar to reflection was given by 0.7 + 0.45 : £an e. Nearly a full those observed in the mineral ktenasite. In both struc- sphere was measured (hk/-range: 7,8,14 - 7,8,8) resulting tures sulphate groups are attached to the sheets of octa- in altogether 3599 reflections. Averaging with Laue hedra through common vertices. In christelite the tetra- symmetry I led to 2214 reflections of which 891 were hedra] [S04] groups are linked to isolated [Zn(H20)402] classified as unobserved, having Fa less than three times octahedra thus forming a three-dimensional structure, the corresponding standard deviation (JFo.The internal whereas in the structure of ktenasite the [SO4] tetrahedra R-va]ue based on Fa was 2.] 'Yo for observed reflections are bonded to isolated [Zn(H 20)6] by a system of and 7.3% for all reflections. hydrogen bonds. Due to the small size and irregular shape of the crystal it The relationship of christe]ite with other minerals is was not possible to approximate the crystal by faces and pointed out and discussed. thus an experimental absorption correction according to North, Phillips and Mathews [9] using It'-scans (measured Introduction every 10 )was applied. The minimum relative transmission was found to be 72.60%, the maximum was 99.70%. Christelite was first found in the San Francisco mine, Sierra Gorda, northeast of Antofagasta, 2nd region in Chile. Associated minerals are paratacamite, anglcsite, Structure determination hemimorphite, quartz and one more unidentified mineral. Christelite was described by Schluter, K]aska, Adiwi- The structure was solved in space group pI using direct djaja and Gebhard [12] who reported optical as well as methods with the program SIR92 [1]. The atomic posi- crystallographic data. The unit cell parameters given are tions of the heavy atoms as well as the positions of the sulphur and oxygen atoms were determined this way. a = 5.415(1) A, h = 6.338(1) A, c = ]0.475(1) A, x = The coordinates of the atoms and the individual 94.38(1)', /3 = 90.08(1)', ./ = 90.24(]) (space group PI) and the idea] formula assumed is Zn3Cu2(S04)2(OH)6 . isotropic atomic displacement parameters were refined 4 H20. The new mineral has been accepted by the ]MA by full-matrix least squares cycles using the program Commission on New Minera]s and Minera] Names. SHELXL-93 [14] to an R(F)-va]ue Rl = 0.065.1At this So far no other occurrence of christelite has been stage of refinement the difference Fourier map showed reported. the positions of all the hydrogen atoms. In further refinement cycles anisotropic displacement parameters for the Cu, Zn, S and oxygen atoms were introduced Experimental and a weighting scheme according to w = 1/[(J2(FY 2) Weissenberg photographs of a small crystal (20 Jim + (a . p)2 + h. P] with P = (max (Fa + 2Fc 2)/3 was x 60 Jim x 60 Jim) showed triclinic symmetry. No extinc- used. The final values for a and h were 0.0528 and 0.47. Correspondence author * Table 1. Positional and isotropic displacement parameters for thc atoms with e.s.d.'s in parentheses. Atom x .I' :: U,q Znl 0 0 0 0.0145(2) Zn2 0.51228(7) 0.24973(6) 0.49511(4) 0.0127(1) Cui 0 0 In/- 0.0110(1) Cu2 0 1/2 1/2 0.0116(1) S 0.7771 (2) 0.7040 0.22146( 8) 0.0126(2) 01 0.7947(5) 0.7289(4) 0.3637(2) 0.0141(5) 02 0.5206(5) 0.6551(6) 0.1854(3) 0.0275(7) 03 0.9370(6) 0.5294(5) 0.1729(3) 0.0246(6) 04 0.8590(6) 0.9034(5) 0.1722(3) 0.0269(7) 05 0.6807(4) 0.0026(4) 0.5889(2) 0.0114(4) 06 0.6829(5) 0.5153(4) 0.5872(2) 0.0125(5) 07 0.1381 (5) 0.7641(4) 0.5888(2) 0.0127(5) 08 0.7246(5) 0.2267(4) 0.0160(2) 0.0172(5) 09 0.2469(5) 0.1890(5) 0.1179(3) 0.0242(6) HI 0.242 0.690 0.944 0.05 H2 0.344 0.731 0.052 0.05 H3 0.217 0.312 0.146 0.05 H4 0.410 0.195 0.098 0.05 H5 0.123 0.772 0.666 0.05 Fig. I. Projection of the structure of christelite parallel [100]; H6 0.687 0.006 0.677 0.05 H7 0.697 0.517 0.680 0.05 octahedra around CuI, Cu2, Znl and [S04] tetrahedra are shown; Zn2 atoms appear as large open circles; polyhedra around Zn2 are not drawn for reasons of clearness; hydrogen atoms are represen- tated by small circles; the hydrogen bonding system is shown (drawn The positional and displacement parameters of the with STR UPLO [3]). hydrogen atoms were not refined. The final RJ value was 0.033 for 1436 data> 40' and Sulphate groups link the sheets of octahedra to isolated 0.070 for all 2031 data; wRz was 0.089 and S = 0.969.2 [Zn 106] octahedra thus forming a three dimensional Since in the final result no indication was found that structure, which in addition is held together by a system the structure was non-centric, the chosen space group pI of hydrogen bonds. was assumed to be correct. The [Cul06] and [Cu206] octahedra have nearly 21m Final atomic positional and isotropic displacement symmetry, the [Zn206] octahedron has symmetry 1. parameters are given in Table 1.3 In the coordination sphere of CuI and Cu2 the equa- torial plane is formed by oxygen atoms belonging to hydroxyl anions (OS, 06, 07) whereas the oxygen atoms Description and discussion of the structure (01) at the apices belong to the sulphate tetrahedra. For Cu 1 the equatorial bond distances range from Fig. 1 shows a projection along [100] of the crystal 1.964 A-1.970 Aand the axial bond distances are 2.415 A. structure of christelite. The coordination polyhedra of Znl, CuI, Cu2 and sulphur are shown. Coordination Table 2. Bond distances in A in the coordination polyhedra with polyhedra around Zn2 are not drawn for reasons of e.s.d.'s in parentheses." clearness. Bond lengths within the polyhedra are given in Table 2. Znl - 08' 2.073(3) Zn2 - 05' 2.047(2) The main feature of the structure are continuous sheets 08" 2.073(3) 06" 2.069(2) parallel (001) of the octahedrally coordinated Cu 1, Cu2 04''; 2.091 (3) 07'" 2.087(2) 04" 2.091 (3) 06 2.087(3) and Zn2 atoms. Ideally the symmetry of the sheet is 09 2.122(3) 05 2.120(2) trigonal yet due to the pronounced tetragonal distortions 09'" 2.122(3) 01" 2.224(3) of the octahedra the sheets are corrugated and the symmetry is reduced. CuI - 05' 1.964(2) Cu2 - 06" 1.945(2) 05;' 1.964(2) 06;' 1.945(2) The distortions of the octahedra can be explained on 07"11I 1.969(2) 07 1.994(3) the basis of the Jahn- Teller effect and give an important 07";' 1.969(2) OT'li! 1.994(3) hint for the identification of Zn and Cu atoms (see below). 01"; 2.415(3) 01'" 2.387(2) OIL, 2.415(3) Old 2.387(2) S 02 1.464(3) 2 wR2 = [2: [w(Fo2 F,2)2]/2:[w(Fo2)2W/2and - - 04 1.467(3) S F,2)2]/(n p)]1!2 with n number of reflections = [2: [W(Fo2 - - = 03 1.469(3) and p total number of parameters. = 01 1.489(3) 3 Additional materials to this paper can be ordered referring to the no. CSO 404835, names of the authors and citations of the Symmetry operators for generating equivalent atoms. 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