Canadian Mineralogist Yol.29, pp. 385-390(1991) THECRYSTAL STRUCTURE AND THERMALEXPANSION OF TUGTUPITE,Nar[AlrBerSirOro]Cl, ISHMAEL HASSAN* ANDH. DOUGLAS GRUNDY Deportmentof Geologt,McMoster University, Hamilton, Ontario L8S4MI ABSTRACT INrnooucrtoN The crystal structure of tugtupite, ideally Tugtupite is tetragonaland has the idealizedfor- Nas[Al2Be2siso2.p,]C12, has been refined in spacegroup .I4 mula Nas(Al2BqSlO2)Cl2 (Dand 1966, Sdensen el to an R index of 0.023for 621 observedreflections meas- ol. l97l). The structure of tugtupite is isotypic with ured on an automated single-crystal four-circle X-ray that of sodalite(cubic), as is that of mineralsof the diffractometer using MoKo radiation. The framework 7 helvite group. The tugtupite framework may be (T representsAl3*, Bd+, and Sia+) are fully cations regardedas intermediatein composition betweenthe this order lowers the cubic symmetry of many ordered, and (AloSkOdt hel- sodalite-group minerals to tetragonal symmetry for tugtu- framework of sodalite and that of of tug- pite, a sodalite-groupmi^neral. The "sodalite" cagein tug- vite (Be6Si6O2/12-.The tetragonal symmetry tupite contains[Na0.611r" clusters. Large Si-O-Be angles tupite is the result of Z-cation ordering (Zrepresents occur in this structure; smaller Si-O-Be angles occur in Al3+, Bd+, and Sia+). helvite-group minerals, because the cages. contain Dafi (L966)determined the spacegroup /? for + [(Mn,Fe,Zn)a.S]6 clusters,whose large effective charge tugtupite by utilizing precession and Weissenberg accountsfor the smaller angles.The thermal expansionfor photographs, and the structure w€rsrefined with film tugtupite is modeled using the DtrS program; the expan- data and the isotypic relationship with the sodalite rotatrons of the 704 tetra- sion is controlled mainly by stnrcture. Interest in tugtupite arisesprimarily from hedra, which are mainly causedby the expansion of Na- result from a fra- Cl bonds and nearly constant Na-O bonds. the detailed structural effects that mework that consistsof three different T cations. Keywords: tuglupite, crystal structure, thermal expansion, In this study, we set out to refine the structure of sodalitegroup, helvite group. tugtupite to obtain better structural parametersfor comparison with structural data for sodalite- and SoMMAIRE helvite-group minerals (Hassan & Grundy 1983' 1984,1985, 1989, 1991, Hassan el a/. 1985).This Nous avons affin6 la structure cristalline de la tuglupite, comDarisonleads to an evaluationof the structural dont la formule id6ale est Na6[Al2Be2SisO2a]C12,dans le effects that arise from different 7 catidns, interstitial groupe .I4 jusqu'i un residu R de 0.023 en utilisant spatral cation (Na+, Mn2+, Fd+, Zrf+), and anions (cl-, 621 r€flexions observ€es(diffractombtre automatisd,rayon- * * OH-, H2O). An opportunity also ari$esto test nement Mo,lfa). Les cations 7 de la trame (Al' , Bez et S?, Sia+) sont complbtementordonn€s. C'est ce degrdd'ordre the applicability of the d-p zrbonding model to the qui r€duit la symdtrie cubique de plusieurs membres de la sodalite-groupminerals (e.9., Cruickshank 1961, famille de la sodalite comme la tugtupite d une symdtrie Brown et al. 1969,Gibbs er ol. 1972).The thermal t6tragonale. La cagetypique de la sodalite contient, dans expansionof tugtupite also is rationalizedin terms la tugtupite, un groupement[Nan.gq3+. Les anglesSi- of its crystal structure, and the mechanismof expan- O-Be sont grands dansla tugtupite; ils sont plus petits dans sion is comparedto that in sodalite-groupminerals les mindrauxdu groupe de la helvite parceque le groupe- (Hassan& Grundy 1984). ment [(Mn,Fe,Zn)0.516+de la cagepossbde une charge effectiveplus 6levee.L'expansion thermiquepeut Otrerepro- ExPsnttvlrNTal- duite par le logiciel DlS. L'expansion serait due surtout rotation des tdtrabdres IOa, d€pendlargement de h la eui in inves- l'expansion desliarsons Na-Cl, la longueur desliaisons Na- The specimenof red tugtupite used this O derneurant d peu prbs constante. tigation is from Ilimaussaq, Narssaq Kommune, South Greenland(Royal Ontario Museum #M3nn). (Traduit par la R6daction) The chemicalcomposition (Table l) is taken from Dand (196Obecause both samplesare from the same Mots-clds: tugtupite, structure cristalline, expansion ther- locality; we assumethat the composition of Dand mique, famille de la sodalite, famille de la helvite. (1966) is repre$entative of our sample. Cell parameters,determined by least-squaresrefinement *Present address: lnstitute for Materials Research, of fifteen high-angle reflections automatically cen- McMaster University, Hamilton, Ontario L8S 4Ml. tered on an automated four-circle single-crystal X- 385 386 THE CANADIAN MINERALOGIST ray diffractometer, are presentedin Table l, together Reflectionsallowable in spacegroup /4 (i,e., h -r with other information pertaining to X-ray data col- k + I = 2n) were collected from two octanls of lection and refinement. reciprocal spaceto a maximum 20 of 65o. A total The intensity data were collected from a cleavage of l4l3 intensilieswere measlued to give a data set fragment mounted on a Nicolet P3 diffractometer. of 647unique reflections, of which 621were classed as observed(Table l). The data were correctedfor Lorentz, polarization, background effects, and TABLE1 . oHEMICAL@MposmoHl . cRysrlt oatn2. lt.to sphericalabsorption (Table 1). All crystallographic INFOFMA'IIONON DATACOIIECTION FOR TlJGTUPITE calculationswere made using the XRAY76 Crystal- Oddo Un % Cofl @rd6rnsr Mb€lall@ lographic Programs (Stewart 1976). Ar2% 11.15 Al 2.03 a(& &640(1) STRUCTURE RSTTNBN4SNT 902 51.58 Sl 7.s c(A) 8,873(1) B4 5.40 Bs 2.@ v 63) Initially, the positional parametersand isotropic N%o 6.52 Na 7.e DerEfry€lc. Gmj Y K2O o.12 K 0.02 Cryelsbs (m) o.iu,o.,o temperature-factorsof Dand were used, including MgO O.m Mg 0.05 xo26 those for (fully ordered)Al, Be, and Si atorns,and g'7.ao 1.$ fr(m-]) e.5o atomic scattering factors for neutral atoms were s _0.s? s 0.@ gR o^ taken from Cromer & Mann (1968).A full-matrix 101.58 lvladnm 29 650 least-squaresrefinement was made by varying the o-ct,s l,9g 0< h,k,t3 13 atomic positions, isotropic temperature-factors,and Total .g!9 Tolalm. ot inemltlss No.of@huci*doE A7 Chqnlel Fomula No. otnonsq!tu lFol>3d lFl el rABtE 4. rN'rERAToMrcDrsrANcEs (A), ANGLES AND u8€d h retr|mnl Fhot'R 0.023 e ), VALENCESUMS (v.u.) FOF IUGTUPm N%t&Bs23lso2ilCt2 FbEl 4{ 0.030 'Ohemlcalarulysb trom Da|p (lS). AlO4Tstrah€dron B€O4 TstEh€dron lSpae qrcuprA; Z - 1; Radmon/Mshrctrdtr - Mo/C; Mot{r - 0.71069A Af-o3 4\ 1.748'(21 Bo-O2 4x 1.601(2) -:11rol -lr"l)p Fol;'\ - Ew(lFol- tFcl)2/:wlFol2l%,w - r. o3o3 4x 2.845(3) Q2-O2 4x 2.633(3) ln-Bas€d on Al + Bo + Sl = 120 2x 2a72p't 2x 2f,29) Mean L& Mean ?,6 os.Al€34x 109.0(1) O2-B+O2 4x 107.7(1) 2x 110-5(11 2x 113.2(1') TABLE2. POSMONALOCCIJPANCY, AND ISOTROPTC IHERMAL Moan 1495 Msan l_095 pnnauEreRs62xro1 SlO4Tofah€dron !,laCoordlrdlon Aom Sne Oe. x ubo sf€1 1.u4(4 Na€l 2.707(11 €1* 1.U7(2) 2.370(3) A 2(d) 1.0 o 1/2 3/4 76(41 -o2 1.581(2) -o2 2.3orl(3) Bo 2(cl 1.0 o 1/2 114 98(14) €3 1.6@(2) -o2. 2.603(3) sl s(s) r.0 0.0127(1, 0.2533(1) 0.4958(r) 74(1', Moan l.620 o3 2.306(3) 01 8(s) 1.0 0.1504(3) 0.1341t(2) 0.u17(2) 1A@'l o1€1r 2.dt2(31 ol-Nao 115.2(1) '1.0 02 8(sl 0.un(21 0.0385(3) 0.6488(2) 119(4) a2 2.587(31 a2 110.6(1) @ 8(s) 1.0 o.4a(4 0.1486(2) 0.132(3) 120(4) €s 2.640(3) -o3 98.0(1) Na 8(S) 1.0 0.15dt(2) 0..t972(2' 0.1818(2) 188(3) o1.€2 2.637(3) o2-Na-ct 12,-8(11 O 2(a) 1.000 o 234(3) 03 2.601(3) -o3 se.5(1) o2-o3 2.723F) olNa-cl 106.1(1) Mean zW BdiglngAngles ol€t€1r 108.6(1) sr€l€r 140.8(2) T BLEs. ANrsorRoptcTEMpERAluRFFAcronsl6 ro! 42 106.7(1) SlO2-Be 143.6(1) 03 108.5(1) sr€$Ar 135.30) Alom U1.t u2 ugg utz u.t3 ua o1.€to2 109.5(1) T-Tdlslanc6 o3 106.0(1) sl-Ar 3.100(1) AI 73(5) 7S 74(81 0 00 o2€l€3 117.2(21 sr+r 3.105(11 BS 86(18) 86 ra(34) 0 00 Msan l_09,4 slBs 3.051(1) sl 71(31 63(3) 86(3) -2(21 -2(3) "3(3) ol 126(e) 116(e) 128{e) 8n 10(8) 1c4 Bond-t,algncssums (v.u.) Al=4x0.7@ =3.076 02 107(8) 119(8) 132(e) -3(6) -35(8) 4(8) Bg=4x0.5@ =2.035 @ 112(81 114(8) 135(e) -1(6) 6f4 38(s) Sl - 0.947+0.940+1.18+1.041 = 4.051 Na zffjrI 160(61 1$(6) 7(5) 24(5) 12(5) tla = 0.25+0.216+0.269f0.115$0.201= 1.041 2n(41 244Q1 0 00 Ol = 0.947+0.91O10.216 .2.l(rll 02 - 1.123{0.509+0.259+0.115 = 2.@6 03 = '|.041+0.769+0.20 1 tUU- up1-zr2i.lr.,tl+upf +Uof +zu.,ltk+2uftht+2uztlll THE CRYSTAL STRUCTURE OF TUGTUPITE 387 , l-or' c Frc. l. Stereoscopicprojection of the framework of tugtupite showingthe "sodalite" cageand the ordering of the Tcations.