Carwdian Mineralogist Vol. 16, pp. 131-137 (1978) KESTERITE,Cu2(Zn,Fe)SnS+, AND STANNITE,Cuz(FeZn)$nsa, STRUCTURALLYSIMILAR BUT DISTINCT MINERALS* S. R. HALLt, J. T. SZYMA(SKI eIn J. M. STEWART Mineral SciencesLoboratory, CANMET, Departtnent of Energy, Mines & Resources, 555 Booth Street, Ottawa, Ontario KIA ocl AssrRAcr (12,/2,0)et S en 8g (0.7560(2),0.7566Q),0.8722(2)). Dans la structure de la stannite, les atomes se si- The crystal structure of kesterite from Oruro, tuent diff6remment:Cu en 4d (0,/2,/e), (FeZn) en Bolivia has been determined by single-crystal X-ray 2a (0,0,0),Sn en 2D(Yz,r/2,1/z) et S en 8t (0.7551(1), diffraction metlods and refined to an R value of 0.7551(1),0.8702(l)). Les diff6rencesstructurales 0.0,14 (atl data). Th_e mineral is tetragonal, a qui r6sultent de l'emplacementdes atomesde cuiwe 5,427(l), c 10.871(5)4, Z=2, space group /4 and expliquent pourquoi ces deux min6raux ont des composition Cu1.u(Zne.7sFeo.1rCd6.e1)Snq.esSa.oo. The mailles et des propri6t6s optiquesdistinctes. crystal .structure of the coexisting mineral sfannils Clraduit par la R6daction) has been refined to an.R value of 0.025 (all data). Stannite is tetragonal, a 5.449(2), c 10.757G)4,, Z-2, space grotp I42m and composition Cu1.sg- INrr.opucrroN (Fee.s1Zne.1sCdq.o2)Sns.qnSa.6s.The kesterite structure is characterized by a cell that is pseudocubic The minerals stannite and kesterite are recog- Qa = c). The Cu atoms are in the separate positions nized as separatespecies because of their differ- 2a (0,0,0) a\d2c (0,Vz,Ye).The (tu,ps;, Sn and S ent Fe to Zn compositional ratios, and their atoms are in positions2d (/2,0,/e),2b (Vz,Vz,O)and distinct optical and physical properties. These and 89 (.7560Q), .7566(2), .8722(2)), respectively. minerals occur at a large number of localities, In the stannite structure the Cu, (Fe,Zn), Sn and S often as twolphase intergrowths. The composi- atoms are in positions 4d (O,Vz,Yq), (0,0,0), 2a 2b tional and crystal data for a number of tlese (Yz,/z,Vz) and 8i (.7551(1),.7551(l), .3702(1)), minerals from different localities are being com- respectively. The structural differences due to the piled (in positioning of the Cu atoms account for the distino by Kissin & Owens prep.). The results nnil gells and optical properties of these two min- of their study tend to discount the possibility that erals. kesterite and stannite are members of pseudo- binary solid solution series, as was originally suspectedfrom the wide compositional range of SoMMAIRE Fe and 7n, because their cell dimensions are largely independent of. Fe/ Zn variation, La structure cristalline de la kesterite a €t6 d€- In order to confirm that kesterite was indeed termin6e sur un cristal d'Oruro (Bolivie) de compo- structurally distinct from a coexisting stannite, sition Cur.ee(Zne.6Fe6.2eCdo.or)Sn6.eeSa.n6;elle a 6t6 crystals were selected for X-ray structure anal- jusqu'i (en affin6e un r6sidu de 0.044 utilisant tou- ysis from the specimens analyzed by Kissin & tes les rdflexions). T6tragonale, avec a 5.427(l), c Owens (in prep.). The structure of stannite was 10.871(5)A, Z-2, elle possede la sym6trie t4. On (1934), a aussi affin6, jusqu'au rdsidu R=0.025 (sur don- determined by Brockway who assumed n6es complbtes), la structure d'une stannite co-exis- a stoichiometric composition CuzFeSnSa,but the tante de composition Cu1.ee(Feo.g1Zn6.1sCdo.o2)Sn1.ss-structure is redetermined here in order to pro- Sa.s6,t6tragonale avec a 5.449(2), c 10.757(3)A, vide a suitable comparison with that of kesterite. Z-2, de groupe spatial 142m. llne maille quadru- ple de la kesterite est pseudo-cubique (2a=c). Les atomes Cu occupent deux positions distinctes 2a EXPERIMENTAL (0,0,0) et 2c (O,r/z,Ye)i les autres atomes se placent comme suit: (Zn, Fe) en 2d (Y2,0,/s), Sn en 2D Kesterite An irregular crystal fragment of kesterite of approximate dimensions 0.25X0.10x0.06mm *Minerals ResearchProgram, ProcessingContribu- tion No. 57. was extracted from specimen 2R(2) Kissin & tPresent address: Crystallography Centre, Univer- Owens,in prep.), from Oruro, Bolivia. Gandolfi sity of Western Australia, Nedlands 6009, Western powder photographs of the fragrnent show that Australia. it is a single phase, and that it contains none of t3L 132 THE CANADIAN MINERALOGIST TABLE1. CRYSTALDATA K.este.rit.e Stannite Source: Oruro,Bolivia 0ruro,Bolivia gr. 2R(2),(Kjssin & Owens,in prep.) gr. 2R(3),(Kissin & 0wens,in prep.) Composi : (F"0.812n0. 5n --(friii6liobeti on cur.gB(2n0. 73F"0. 2gcd0. o1)Sno. 99s4. 00 c'1. 99 18cd0.02) 1. 00s4. 00 analysis ) CelI dimensions: a = 5.427(I), e = 10.871(5)i a = s,44s(2), c = 10.757G)"A tematic absences: h+k+L= zyL+I h+k+t = 2n+1 Spacegroup: 14 (#82), z = 2 rlzn (r1,2r),z = 2 Absorption : u(Moro)= 151.3cm-1 u(Morro)= 147.5cm-1 Data: (I/U Or LwarospnereJ (1/16of Ewaldsphere) 1288measured 3 times 692measured 3 times 1119with I>o(I) 684with I>o(I) the stannite with which it soexists. Precession monitor tlle crystal alignment and instrument photographs show the crystal to be single, un- stability. lwinnsd, and to have a diffraction pattern with The three octants of data were merged after systematically absent reflections when h+k+l= the application of generalized Gaussian absorp- 2ni1,, The absencesand the general intensity tion corrections (Gabe & O'Byrne 1970) into an equivalences of the pattern suggest the Laue asymm€tric data set containing the mean net in- group 4/ mmr?. In turn, this limits the space tensity Io"t atrd the r.m.s. deviation o(I). Negative group to i42m because of the as$umed sphaler- net intensitieswere set to zero. Of the 1288 inde- ite-like arrangement of sulfur and metal atoms, pendent reflections, 1119 had mean intensities which usually occurs in this type of structure. greater than <r(I) and an overall agreementfactor Becauseof the close correspondenceof. hkl ar;d >At>I of 0.054. This agreoment factor is /cil intensities, this seemed from initial exam- significantly higher than that achieved subse- ination to be the only choice (Hall et aI. 1975). quently for stannite (0.021), and reflects the Later, however, tle refinement of a kesterite difficulty in describing the very irregular shape structural model based on this space group and smaller size of the fragment in terrns of raised serious doubts about its applicability and plane faces for the purpose of applying absorp- suggested that the correct space-group is /4. tion corrections. Structure factors were derived This will be discussed further below. In this by application of Lorentz and polarization fac- section only the last data collection involving the tors with q(D set at Vzq(I) (I.Lp)-*. Laue group 4/m and spacegroup 14 will be de- scribed. The kesterite crystal was oriented on a Picker Stannite 4-circle automatic diffractometer by the best least-squaresfit of the diffractometer angles for A fragment of stannite 0.29x0.L7x0.06mm 40 reflections, assuminga triclinic cell. The best was extracted from an area designated as gtain fit was obtained for the cell dimensions shown 2R(3) by Kissin & Owens (in prep.), adjacentto in Table 1. The errors shown represent 3.o as the kesterite grain 2R(2) used in the above derived from the least-squaresmatrix. analysis. Gandolfi and precession photographs The intensities of the hkl. hEt ana nki octants show the fragment to be homogeneous and a of data were measuredto a 20 limit of 115". single untwinned crystal. Diffraction intensities using graphite-monochromatized MoKa radia- confirmed the space group as i-42m @rockway tion. Measurementswere made inthe 0/20 mode 1934). The crystal was aligned on a Picker 4- at a 20 scan rate of two degreesper minute and circle diffractometer and its cell dimensions de- with a scan width adjusted for dispersion (2.40 termined by a least-squaresfit (Busing 197O) of to 3.48'). Background counts were. measured the 20, 1 and or angles for 20 reflections in the for 30 secondson each side of the scan. and the range 67"120<72o. The same procedure used intensities of three linearly independent reflec- for the kesterite data collection was ado,ptedfor tions were recorded eyerv 50 measurementsto the measurement of three separate segments KBSTERITE AND STANNITE 133 (each L/L6 of tle Ewald sphere) of stannite in- tensities. The seg ents collected were hkl, khl and khl with h>k, and they were merged into PrcposedModels wlth ReflnedAverage Temperature Factors an asymmetric data set of 692 reflections. Of and AgreenentValues tlese, 684 had mean net intensities above o(I), and an overall agreement factor )AI/X of (esterlte Stannlte 0.o21. fi l'lodel 1 llodel 2 i-42n 'oos i tion posltion Atom B(A'?) Aton B(i'?) Arom B(i'?) Srnucrunr Sor-urroN AND RBFnIEIVTENT 2q (0,0,0)Zn,Fe Cu I.44 24 (0,0,0) Fe,zn 0.93 (!,rr,o) sn 0.55 Sn 0.65 b (\,\,0) sn 0.78 Kesterite 2c (0,!,k) cu Cu L.29 4d (0,k,!) cu 1.55 u (L,o,ra) Cu 0.99 Zn,Fe 1.U 8i (x,x'z) s 0.93 The consistently stoichiometric proportions of Cu, (Zn,Fe), Sn and S in kesterite for the range 89 0.85 s 0.85 of specimensand locations studied by Kissin & Owens (in prep.) suggestthat these atoms fully R (al1 data) 0.045 0,044 .P (a] l data) 0.025 occupy specific sites in the structure.