73

The Carudian M ineralo gist Vol. 34, pp.73-78(1996)

THECRYSTAL STRUCTURE OF CLINOATACAMITE. A NEWPOLVMORPH OF Gu2(OH)3Cl

JOELD. GRICE ResearchDivixioq CanadianMu*eam of Nature,P.O. Box 32143, Staion "D", Oxawa.Ontario KIP 6P4

JANT. SZYMANSKI CANMET,Natural ResourcesCarnda" 555Booth Street,Oxawa" Ontario KIA 0GI

JOHNL. JAMBOR Depannznt of Earth Scientes,University of Waerlao, Waerloo, Ontario N2L 3Gl

ABsrRAcr

The crystal structureof clinoatacamite,Cul+(OtI13Cl, has beendetermined and refined to indicesft = 5.2 and wR = 4.9Vo. The strucfirreis monoclinic,spacegoup nlln(1,4),-wirhcellparametersa6.144(l), r 6.805(l), c9.Ll2(l) A, p SS.SS(:)', V 375.7(2)A3, and with Z = 4.T\e structureanalysis was essentialin determfuingthe valencestate of copper(Cu2) and the number of (OII)- anions in the formula. The structure consists of layen of partly occupid edge-sharingoctahedra of Jabn-Teller-distortedtCu(OH)4C121 octahedra parallel to (101). This layer is topologically the sameas that in mica. Adjacent layers of octahedraare offset, suchfhat vacantdites in one sheetalign with occupiedsites in the neighboringsheet Layers are linked by individual, slightly Jahn-Teller-distoriedoctahedra of composition[Cu(OH)o] . The structuresof paxatacamiteand the otherpolymorphs of Cur(OII)3CI,atacamite and botanakite, also arelayered but they differ from the layering of clinoatacamite in topology,composition and srcss-linkage.

Keywords:clinoatacamite, crystal shucture,layer of ocahedr4 polymorph,Jahn-Teller distortion.

SoMr{ens

Nous avons affind la structurecristalline de la clinoatacamite,Cua+(OH)3CI, jusqu'i un rdsidu fi de 5.2Vo(wR = 4.9Vo). Il s'agitdhne structure6saoclinique, ^groupe spatial P21ln (14), dont les paramdtresr6ticulaires sont a 6.1,44(1),,6.805(l), c9.Il2(I) A, B 99.55(3f, V375.7(2) A3,powZ=4. L'6bauchede la structurea6t6 essentiellepourfixerlavalencedu cuivre (Cu}) et le nombre d'anionsOH- dans la formule chimique. La structureest faite de feuillets paralldlesd (101), compos6s d'octabdresdifformes [Cu(O[I)aClr] partiellementoccup6s, partageant des a€tes; cesoctaBdres sont difformes i causede I'effet de Jahn-Teller. Ces feuillets sort topologiquementidentiques h ceux qui caritctdrisentles micas. Les feuillets adjacentssont d&al6s, de sorteque les lacunesd'un feuillet sontalign6es avec les sitesoccup6s du feuillet adjacent.Ces feuillets sont li6s par des octabdresindividuels de cogposition tCu(OII)61,l€gBrement difformes, encore A causede I'effet de Jahn-Teller. Les structtnesde paratacamiteet despolymorphes de Cu2(OtlrCl atacamiteet batallackitepossbdent aussi ces feuillets; toutefois, elles ditldrent de la structurede la clinoatacamitedans la topologie,la compositionet I'interconnexiondes feuillets.

Clraduit par la R6daction)

Mots-cl6s: clinoalacamite,stusturg sristalline,feuillet d'octabdres,polymorphe, distorsion, effet de Jahn-Teller.

INTRoDUC"iloN tion of Cu by Zn for stabilization(Jambor et al. 7996). The crystal-structure analysis reported here was Clinoatacamite (monoclinic) from Chuquicamat4 undertakenin order to understandthe crystal-chemical Chile, has been describedas the third polymorph of relationshipsamong these fqur mingrals, Cu3+(OH)3Cl (Jambor et al. 1,996); ulasimite (orthorhombic) and botallackite (monoclinic) arc the Etparatacamite (rhgmbohedral) is not a fourth polymorph of The small amormtof holotype clinoatacamiteavail- Cua*(OH)3CI,as this mineral requirespartial substitu- ableprecluded standard chemical analytical techniques 74 TIIE CANADIAN MINERAIPGIST capableof differentiating the valencestate of Cu and the four asymmetricunits of reflection data. the determination of H2O. The structure-analysis method (Hawthorne& Grice 1990) establishedthese Cnvsrar,-Srnuc"nrnsANALvsrs quantities; the fonnula is Cua+(Olt)3C1.Electron- microprobe analysis (Jambor et al. 1996) of the Normalized structure-factor statistics indicate a material gave CUO74.7, Cl 16.5, (H2O from structure centrosymmefic space-group.The E-map coordinates analysis L3.5), sum 104.7, less O = Cl 3.7, lotal were assignedto appropriatescattering curves, three 1.01.0 wt.Vo. Zinc and Ni were not detected. Cu. one Cl and three O atoms. This sffucture model Based on O + Cl = 4, the empirical formula is refinedroR=6.8Vo. Cu1.e6o3.03H3.1tCln.r.The ideal formula Cu2(OH)3C1, In the final least-squaresrefinemen! the siles of all requiresCUO 74.49, Cl 16.60 and HrO 12.66,sum atoms were refined with anisotopic displacement- L03.75,lessO = CI3.75, total 100 wt.Va.Itis evident factors to final residualsof. R = 5.2Voand wR = 4.9Vo. that within the limits of experimentalerror, the malerial The addition of an isotopic extinction-correctiondid studiedis ideal, end-memberclinoatacamite. not improve tle refinement. Owing to tle poor A crystal fragmentof type clinoatacamitewas used agreementamong symmetry-relatedreflections, Ra, = in the collection of X-ray-dilfraction intensity data. l2.lvo.the stacturewas solved and refined in Pl. This Single-crystal precession photographs indicate the refinement,with isotropic displacement-factors,had a unique space-groupP21ln (1,4), on the basis of considerablypoorer residual factor, with R = l5.5%o. systematicabsences ofreflections. Intensity data were The lower-symmetrystructure model was testedusing collected on a fully automated CAD four-circle MISSYM (Le Page 1987) and found to contain diffractometer operated at 50 kV, 26 mA, with an apparent symmetry of 211m.This symmetry graphite-monochromatedMoKcr radiation. is consistent with the Cu atomic positions, but A set of 44 reflectionswas usedto orient the crystal the O atoms obey space-gtoup symmetry P21lle. andto refine the cell dimensions.Four asymmetricsets Refining the sfiucture rn F2ylrn with an:isotropicdis- of intensity data were collectedup to 2Q= 60ousing a placement-factorsresults in residualfactors R = LL.3Vo 0:20 scan-mode,with scan speedsof approximately and wR -- l3.8Vo, and all of the O atoms have non- Lolminute. Data pertinent to the collection of the positive definite displacement-factors. Thus it is intensity data are given in Table 1. evident that F21ln is the correct space-groupand that Datareduction,using the NRCVAX setof computer the rather poor refinement is attributable to the programs(Gabe et aI. 1989), included correction for problems inherent in an absorptioncorrection of an background, sealing, Lorentz and polarization and elongate crystal fragment. tn the final AF-synthesis, linear absorption.For the absorptioncorrection, four residual electron densities of 2 e-lA3 remained, but intense diffraction-maxima in the range 25 to 53o none of these could be satisfactorily assignedto H 20 were chosenfor y diffraction-vectorscans after the atoms. The final positional and displacementpara- methodof North et al. (L968). Structuredetermination meters for the clinoatacamitesfructure rn P21ln we and structure refinement were done using of the given in Table 2, and selectedbond-lengths and angles, SIIELXTL (Sheldrick 1990) package of computer in Table 3. Observedand calculatedstructure-factors programs.The i:regular shapeof the crystal precluded and anisotropic displacement-factors have been a good absorption-correction,and becamethe limiting submitted to the Depository of Unpublished Data factor in the structurerefinement. This problem in the CISTI. National ResearchCouncil of Canada Ottawa, datareduction is evidencedby a mergingR of l2%ofor CanadaK1A 0S2.

TABLE1. CUNOATACAMITE:STRUCTUREOETERUNAION DATA TABLE2 CUNOATACAMITE:ATOMIC GOORDINATES, ISOTROPIC DISPLACEMENT

ldoal fomula: Cu?(Ol03Cl a = B.laa(l) 4 Atom x y z U(A1x'to2 BVsr Spa@gmup: nlln b ' 6.805(r)4 Crystalstro: 0-14x 0.08x0.04 mm c = 9.112Q)A Cut o 1r2 1n 1.44(4) 1.SE F .99.55(3)" 000 r.8q4) 2.00 RadJMon.: Mo/graphJte Y.375.7(2) A3 cu3 0.2588(2) 0.A€40) 0.2185(2) 1.55(3) 2.02 tt 11.9mm"' Z-4 o1 02e98(10) 0.2002(10) 0.5470(8) 22(2) 1.18 Tdd rsf. 4186 0.41e0(8) -0.fi4r(8) 0.7w(8) 2.2Q) 124 Mln. transmlsslon 0.037 F unlqua1092 o3 02598(8) 0.8792(8) 0.5372(8) 1.e(4 127 Max. llansmbslon Fo>86(ne74 cl 0.1116(3) -0.0038(3) 0.3ff)E(2) 1.87(0 o.37 Fhal R s 5.2oi nrrr"Bn(lF,l-F,b2natr|fn, r"to'(rJt nnalwRe 4.99/. t Eond-vatenco6urns (%u.)ushg ths paramsto's ol Br6ss & Olcetfo (1991). TIIE CRYSTAL STRUCTTJREOF CLINOATACAMITE 75

TABLE3, CUNOATACAMITE:SELECTED INTERATOMTC DISTANCES (A) AND BONDANGLES (O)

cu1 polyhedron Cu2 Dolvhedron cu3 Dolyhedron

Cul.O'l 2.288(6)x2 Cu2-Ol 1.948Q)x2 cu$ol 1.934(8) Cu1.O2 2.050f0x 2 Cu2-O3 '1.9E7(6)x 2 cu&o2 1.975(5) Cu1-O3 1.99'l(5)x 2 Cu2-Cl 2.766(2)x2 cu&O2' 1.999(5) cu3-O3 2.015C0 01-Cu1-O2 74.3(2' 01-Cu2-O3 E3.6(2)x 2 Cu$cl 2.7ffi(2) Ol-Cu'l-O2' 105.7(2) 01-Cu2-O3' sa.Ae)x2 Cu3-Cl' z.Ec,4,e) O1-Cu1-O3 75.1Q) 01-Cu2-Cl ss.OQ)x2 O1-Cu1-O3' 10/.s(2) O't-Cu2-Ct 81.0(2)x2 o'l-culo2 98.2(3) O2-Cu1-O3 78.5(2) O&Cu2-Cl 8.4(2)x2 o1-cu3-o2' 83.8(3) O2-Cu1-O3' 141.4Q) O&Cu2-cl' E3.6(2)x 2 01-cu3.cl 100.3(2) Ol-Cu&cl' 80.2Q) cl-ol 3,070r0 o2-cu3-o3 79.9(3) cl-o2 3.0e0(6) o2-cu3-Cl 84.1(1) ct-o3 3.042(6) o2-Cu3-Cl' 100.6(2) o2'-Cu$O3 98.3(3) O2'-Cu$cl 52.8(2) O2'-CulCl' 82.4(1) o&cu&Cl 83.4(2) O$.cu&Cl' 96.3(2)

Dxcp;prroN .qNDDrscussroN that there are three other polymorphsof Cu2(OII)3C1, OF TI{E STRUCTT]RE and the crystal structure has been solved for each; atacamite@arise & Hyde 1986), paratacamite(Fleet The analysis of the structure of clinoatacamite 1975) and botallackite (Hawtlorne 1985). Like permittedthe calculationof bond-valencesums for the clinoatacamiteoeach of these structureshas layers of various a0omicsites. On the basis of the constantsof octahedrabut of differing composition or topology. Brese & O'Keeffe (1991), the sums are: Cul 1.98, Botallackite has a layer of fully occupied octahedr4 ca 2.09,aB 2.02,cl 0,37,01 1.18,02 1.24 and with composition [Cu(OtI)aCl2] @ie. 2a). Adjacent 03 I.n yz. Thesecalculations allow assignmentof the layers are H-bondedtogether tbrough hydroxyl donors correct valence,Cu2+, to the cation and recognitionof and Cl acceptors(Frg. 2b). In atacamite,the layers OL, 02 and 03 as (OID- aniens.Jls lesultant simplest of octahedra,and their stacking, resemble those of formula for clinoatacamiteis Cul+(OQrCl with Z = 4, clinoatacamite,but the vacant sites in the layer corre- oooctagonal" The low bond-valencesum of the Cl atom is due to spond to a more distorted hole @g. 3). H-bonding. Each Cl atom is H-bonded to all tbree The difference in topology between the layers of O atomsatbond distancesof 3.(X to 3.09A (Table3r. clinoatacamiteand those in atacamiteresults from a Thesebond distancess1e simil2l to the averaeeojl change in composition within the layer. In clino- distance in paratacamite(3.07 A: Heet 1975) and atacamite, both octahedra have the composition botallackite(3.21 A: Hawthorne1985). [Cu(OH)4Clt, whereasin atacamite,the two octahedra The crystal structure of clinoatacamite may be havethe composition[Cu(OIDaCl2] and tcu(OfD5clrl. describedas made oflayers ofpartially occupied,edge- The [Cu(OIDoClr] octahedron in each structure is sharing,Jahn-Teller-distorted [Cu(O]t)aCl2l octahedra (4 + 2)-distort€d,with the Cu{l bonds being longer parallel to (101) @ig. 1a). This layer is topologically than the Cu-O bonds; in atacamite, however, the the sameas that in mica. Adjacent layers of octahedra [Cu(O[I)4C12]octahedron is (4 + 2)-distortedwith two are offset suchthat vacautsites in one sheetalign with apical Cl ligands,and the [Cu(OII)5C11]octahedron is occupied si0esin the neighboring sheet. Layers are (4 + 2)-distortedwith one apical Cl and one apical O linked by individual, slightly Jahn-Teller-distorted Iigand. Paratacamitehas the same layer composition octahedraof compositiontft(Olt)61 @ig. 1b). Eby & and topology as clinoatacamite(Fig. 4a). It is the Hawthorne(1993) classified this type of copperoxysalt interlayer, isolated tcu(OfDol octahedronthat differs mineral as an infinite framework stucture M = M. in the fwo minerals.In the clinoatacamitesfructure. the whereM denotesoctahedrally coordinated cations, and interlayer octahedronexhibits a Jahn-Tellerdistortion, the doublehyphen denotes edge sharing. but in paratacamite, one [Cu(OH)6] is axially In addition to clinoatacamite,it has been assumed compressedwhereas the other is a regular octahedron 76 THE CANADIAN MINERALOGIST

Frc. 1. The structureofclinoatacamite: (a) (101) projectionshowingthe layerofedge-sharingCu(OII)aC|2 octahedra; (b) (010) projectionshowing (101) layersof Cu(OQaCl2octahedra with single Cu(Ot!6 octahedracross-linking layers. The unit cell a

Gig. b). Eby & Hawthorne(1993) remarkedon this octahedralcoordination. Apparently, the crystalused in anomalousoccurrence of symmetrically bonded Cu. the stucture determination (Fleet 1975) was not That parafacamitecontains essentialZn (or another analyzed,and it is probablethat the structuredoes trot oopure" catio& e.9.,Ni) is snongly suggestedby the fact that all correspondto a Cu-bearingcompound. paratacamitecrystals studied to datecontain significant The indications are that paratacamiteneeds to be amountsof Zn or Ni (>2 wt.7o), even those from the redefined, as it is probably not a polymorph of type locality (Jambor et al. 1996). Zinc n a 6-fold Cua(OII)6C12,but a distinct phase of composition '?arata- coordination atomic site usually has fairly regular Cu:(Cu,ZnXOtDoClz.In such a case, tile

Fro. 2. The strucfire of botallackite: (a) t1001projection showing a layer of fully occupiededge-sharing octahedra. (b) t0011 projection showing (1@) layering of Cu(OII)nCl, octahedraand H-bondinglhking layers.The unit cell a < D is outlined. TI{E CRYSTAL STRUCTUREOF CUNOATACAMITE 7',|

Ftc. 3. The structureofatacamite: (a) (110) projection showing the layer ofedge-sharing Cu(Oll)oCl2octahedra;(b) (001) projectionshowing (ll0) layering ofCu(Olf)aCl2octahedrawithsingle Cu(OI!5CI, octahedracross-linking layers. The unit cellacDisoutlined. camite" sftucturewould haveZn orderedat the regular IMA. It would be appropriate that rhombohedral octahedralsite within equipoint position 30. Jambor Cq(Cu,4XOII)6C12,witha13.65 andc 14.0A, space et al. (1996) showed that only 2 wt.Vo 7n was group R3, which correspondsto the holotype from necessaryto stabilizethe rhombohedral(pamtacamite) SierraGorda Chile, andfor which the crystal sfructure structure;thus Zn neednot be the dominantcation in was determined by Fleet (L975), be retained to the 3b site. Sucha redefinitionrequires approval by the designatethe mineral paratacamite.If paratacamite Commission on New Minerals and Mineral Names. is redefined in this way, the following may be con-

Flc. 4. The structureofparatacamite: (a) (001) projection showingthe layer of edge-sharingCu(OII)aCI2 octahedra; (b) (110) projectionshowing (@1) layering of Cu(OH)oCl,octahedra and isolatedCu(OIlu octahedracross-linking layers. The c axis is vertical. 78 TIIB CANADIAN MINERALOGIST sidered as new minerals: 1) compositions between & Gmcs, J.D. (1990): Crystal-structureanalysis CulZn,Cu)(OH)6C12and (Cu,ZnLZn(OI06Cl2,which as a chemical analytical method: application to light 28, 693-702. is the Zn analogueof paratacamite;these compositions elements.Can. Mineral. correspondto those of minerals from the Kafi Kafi JArvGo&J.L., Durnzac, J.E., Ronmrs, A.C., Gruce,J.D. & mine, Anaralg han, and Herminia, Chile, with the Szvrrtefsn, J.T. (1996): Clinoatacarnite,a new poly- latter describedby Kracher & Pertlik (1983); 2) morph of Cu2(OI!3C1,and its relationshipto paratacamite (Cu,Ni)3N(Olt)6C12, which is the mineral of this and *anarakite".Can, Mineral, 34,6l:72. compositionfrom the Carr Boyd dsftsl mine (Jambor et al. 1996), and from Widgiemoolth4 Australia KRAcHR, A. & PRrLI! F. (1983): Zrtrreicher Paratacamit (Nickel et al.1994). Cu3Zn(OI06C12,aus der Hennina Mine, Siena Gorda &ile. Ann. Nanrhist. Mus. Wien ESIL,93-97. Acrlrowr.Blcelvnl{Ts LE PAcE,Y. (1987): Computer derivation of the symmetry elements implied in a structure description. J. AppI. The financial support of a Research Advisory Crystallogr.n,2&-269. Committee Grant from the Canadian Museum of Natureto JDG is gratefirlly acknowledged.The authon . Nrcrs-, E.H., Clom, J.F.M. & Garrnen, B.J. (1994): appreciatethe carefirl reviews and helpfirl improve- Secondarynickel mineralsfrom Widgiemoolth4 Westem mentsof the two referees.Drs. PeterBums and Frank Australia. Mineral. Rec. 25, 283-291,302. Hawthorne,and the Editor, Dr. RobertMartin. Nonnr, A.C.T.. Plmrps, D.C. & Mert$ws, F.S. (1968):A of absorption conection. Acta Rsmwcrs semi-empirical method Crystallo gr. AU, 35L-359. (1991): para- Bn$s, N.E. & O'IGEFFE,M. Bond-valence Pap.rss,I.B. & Hvps, B.G. (1986):The structureof atacamite metersfor solids. Acta CrystallognB47 , 192-197 . and its relationship to spinel. Acta Crysnlbgr. C42, tn7-n80. EBy,R.I( & Hawrronme,F.C. (1993): Structural relations in minerals. copperoxysalt I. Structuralhrerwchy. Acta SHEIDRIC&G.M. (1990): SHELX|I" a Crystallographic Crystalbgr.B/,9,28-56. Computing Package (revision 4.1). SiemensAnalytical Instruments,Inc., Madison,Wisconsin. FL@r,M.E. (1975):The crystalstucture of paratacamite, Cur(OH)rCl.Acta Crystalla gr. 831, 183- 1 87. GABE,E.J., LB PAGB, Y., CturuaNn,J.-P., r .FF,F.L. & Wurrp, P.S. (1989):NRCVAX - an interactivesystem for structureanalysis. J, AppI.Crystallagr. 33,385387 .

Hawrnonrrre,F.C. (1985): Refinement of thecrystal structure Received August I, 1995, rnised manuscript accepted. of botallackite.Mineral Mag.49, 87 -89. September2T, 1995.