American Mineralogist, Volume 62, pages ll29-1134, 1977

Reinerite, Zng(AsOa)2tBr trs€rite with a noveltype of Zn-tehahedral doublechainr

SusRere GHose, Pe.ul BovING,WIlr-Illr A. LlCHe.psLLEAND CHr'Nc WeN Department of Geological Sciences, Uniuersity of Washington Seattle, Washington98 I 95

Abstract

Reinerite,Znr(AsOs)z from Tsumeb,S. W. Africa, is orthorhombic, with cell dimensionsa = 6.092(2),b : 14.407(2),c : 7.811(l)A, space group Pbam and Z : 4. The has been determinedby the symbolic addition method and differenceFourier synthesisand refined by the method of least squaresto an R factor of 0.051 based on 1289 reflections, measuredon an automatic single-crystaldiffractometer. The standarddeviation in Zn-O and As-O bond lengthsis 0.003 and 0.0044 and in O-Zn-O and O-As-O angles0.02". The structureof reineritecontains a new type of Zn-tetrahedraldouble chain, [ZnoOro]-, with two-tetrahedralrepeat and four-memberedrings; thesedouble chains are cross-linked into a three-dimensional framework through corner-sharing of a new type of edge-sharingZn- tetrahedraldimers and two types of trigonal pyramidal arsenitegroups. The averageZn-O bond distanceswithin the two independentZn-O tetrahedraare 1.958and 1.964A.Both the arsenitegroups have the point symmetry m, wilh averageAs-O bond distances1.776 and l.77lA and averaseO-As-O bond aneles98.4 and 96.8'.

lntroduction : 2n and hol, h : 2r present. Of the two possible spacegroups, Pbam and Pba2, the first proved to be In the course of our investigation of the stereo- correct on the basisof an l(z)-test of the measured cheniistryof copper and zinc (Ghose and Wan, 1974; X-ray diffraction intensities. Ghose et al., 1974), we have now determined the A single crystal of light blue transparentreinerite crystal structure of reinerite,Zn3(AsOs)2, from Tsu- was checked for crystal perfection through a trans- meb, S.W. Africa. At Tsumeb, it occursat a depth of mission Laue photograph and then ground to a 800 m in a secondoxidation zone of the lead-zinc- sphere of diameter 0.225(2) mm. The single-crystal copper deposit, in associationwith ,hy- sphere was mounted on the syntex PT single-crystal drozincite, , , , and diffractometer,and the unit-cell dimensionswere re- (Geier and Weber, 1958).In addition to the fined by the least-squaresmethod basedon 15 reflec- configuration of the arsenitegroup, the crystal struc- tions with measured2d values between 35 and 45', ture of reineriteturned out to be of considerablein- using MoKa radiation. The cell dimensions(Table l) terest,because it contains a new type of double chain are in good agreement with those determined by consisting of corner-sharing ZnOo tetrahedra, re- Geier and Weber. All (hkl) reflections within 20 = miniscent of the amphibole-typetetrahedral silicate 65o were measured on the diffractometer by the N-0 double chains, and an edge-sharingZn-tetrahedral scan method, using MoKa radiation mono- dimer. chromatized by reflection from a graphite "single" Experimental crystal,and scintillationcounter. A variablescan rate Reinerite was reported to be orthorhombic with was used, the minimum being l"/min (50 kV, 15 possible space group Pmma by Geier and Weber mA). Out of a total of 1289reflections, 239 were less (1958). Precessionphotographs of a reineritecrystal than 3o(1), where o(1) is the standard deviation of the from Tsumeb revealedextinction conditions as0kl, k measured intensity as determined by the counting statistics. All the intensities were corrected for 1 Structural chemistry of copper and zinc minerals Part III Lorentz, polarization, and absorption factors. It29 GHOSEET AL : REINERITE

Table l. Reinerite:crystal data hk I E Sign 0 16 5 3.24 e Reinerite, Znr(As0r)r: Tsuneb, S. I.i. Africa, NMNH#115409 I lr 5 2.54 f 4 | 22.53 Orthorhonbic, 'ffi c

ai 6.Og2Q); Cel1 conrenr: 4[Znr(AsOa)r1 Signsand symbolsof 153reflections with E > 1.60 were determined.Out of the eight possibleE maps, b: 14.407(2) D: 4.270zcm-3 m" one showed the correct structure in terms of the ct 7.811(1) D-t 4.283 e cm-3 heavyatoms, namely 2Zn and 2 As. The symbolse,f -, -. Cell volune: 685.6(2);3 ! (MoKd) : 209 . 71 cn-1 g turned out to be +, A structure-factorcalcu-

qh.^a Cr^"n. Phm lation with the heavy atoms only yieldedan R factor of 0.27. The oxygen positions were determined from a three-dimensionaldifference Fourier synthesis.The R Determinationand refinementof the structure factor at this stage was 0.21. The structure was re- A three-dimensionalPatterson synthesis was com- fined by the method of least squaresusing the pro- puted. However, due to the interaction of four heavy gram RFINE (Finger,1969), first usingisotropic and atoms, the interpretation of the Patterson map then anisotropic temperaturefactors for all atoms. proved to be difficult. The four heavy-atompositions The scatteringfactors were taken from Cromer and were determined directly by the symbolic addition Mann (1968), correctedfor anomalous dispersion method(Karle and Karle, 1966)using the computer (Cromer and Liberman, 1970).The observedstruc- program MULTAN (Germain et al., l97l). The E ture factors Fo's were weighted by l/o2(F"), where valuesfor all reflectionswere calculated. The signsof o(F.) is the standard deviation of F". A few strong the following three reflectionswith large E values low-angle reflections(e.g. 004, l2l) were strongly were chosento definethe origin: affectedby extinction. These reflectionswith Af' ) 10.0 were excludedfrom the refinement.The flnal R hk I E Sign factor is 0.051 for all (1289) reflectionsand 0.046 1922.94 + excluding l8 reflectionsaffected by extinction. The 3622.75 + shift,/errorat this stageis 0.00.The atomic positional 1772.41 and thermal parametersare listedin Table 2 and a list of observedand calculatedstructure factorsin Table In addition, the application of the ), relationship 3.'?The standarddeviations in bond lensthsand an- indicated the signs of two more reflections(0,0, l0) and (18,2,0)with E values1.90 and 1.65respectively '?To obtain a copy of Table 3, order documentAM-77-058 from to be *, *. The following three reflections were the BusinessOffice, 1909 K Street,N.W., Washington,D.C 20006. assignedsymbols: Pleaseremit $1.00in advanceior the microfiche.

Table 2. Reinerite,Znr(AsO.l: atomic positionaland thermal parameters(standard deviations in parentheses)

Atom R^^ Brrt R, " R. ^ Bzs zn(l) 0 0.5 0.31453 (8) 1.ro(r) L25r(r1) 99(3) 252(e) -6 (6) 00 zn(2) 0.56494(8) o.77eo8(3) 0.78434(6) 1. 04(1) 804(11) 724(2) 361(6) 2(4) -58 (8) -e (3) (1) As 0. 91312(10) 0.87 436 (4) 0.5 0. 94(r) 783(L4) 113(2) 298(8) -26(5) 00 As(2) 0.2230s(10)0.90L26(4) 0 0.97(1) 847(L5) r01 (2) 33s(8) 65(s) 00 o (1) 0 . 3304(8) 0. 0608(3) 0.5 1.34(7 ) 1304(121) 149(18) 352(59) 1s8(41) 00 o(2) 0.3349(8) 0. 2807(3) 0 1.16 (6) 1103(108) L24(16) 338(s8) 8s(38) 'oo 0(3) 0.1519(s) o.L997(2) o.3262 (4) 1.4s(5) 840(70) 2r8(L4) 534(45) s8(29) s3(s0) 162(2r) (4) o 0.0904(s) o .3965(2) 0.r736(4) 1.32(s) r372(82) 98(rr) 456(4o) -43(26) 353(s1) -42(78) xEquivalent isotropic B, calculated from anisotropic temperature factors, tForn of anisorropic tenperarure factor (x105), .*p { - i I h-.t"r|r, ) GHOSEET AL REINERITE gles as well as in thermal ellipsoidswere calculated Table 5 Reinerite,Zn,(Asor),: thermal ellipsoid parameters (standard in parentheses) using the ERROR program (Finger, personal com- deviations munication, 1972).The bond lengths and anglesare in Table 4, and the dimensionsof the thermal ahdla rol df P. with respecE to listed Arom Axls, oo *niltl'u" ellipsoidsin Table 5. The averagestandard deviation +q +b +c in Zn-O and As-O bond lengths are 0.003 and 0.088 90 90 90 0.004A, respectively,and in O-Zn-O and O-As-O r2 0.r02 89(1) r79(1) 90 angles0.02o. r3 0.153 179(1) 91(1) 90 zr(2) rL 0.r03 107(3) 79(4) 20(4) Description of the structure rz 0.r15 99(4) 161(4) 81(4) !3 0.L25 161(4) 84(4) r08(3)

The crystal structure of reineriteis a three-dimen- rL 0.096 90 90 0 framework, consistingof three distinct struc- x2 0.107 71(5) 161(5) 90 sional T3 0.L23 161(4 ) ro9(4) 90 tural components: (a) dimers of edge-sharing As(2) rI o.097 114(1r) 155(11) 90 r2 0.102 90 90 r80 0.13r Ls6(2) 66(2) 90 Table 4 Reinerite,ZnlAsO.),: interatomic distances(A) and 0(1) !L 0. 104 90 90 0 angles(') (standarddeviations in parentheses) 0.108 61(105) 29(105) 90 r3 0.169 151(8) 61(8) 0 lhe Zn(1) - Tetrahedton 0(2) TL 0.102 90 90 r2 0.r07 7L2(7r) 158(71) 90 - - zn(1) - 0(1)(x2) 1.983(3) 0(1) zo(1) 0(1') 86.r(1) r3 0.149 158(r1) 68(11) 90 zn(1) - 0(4)(x2) 1.933(3) 0(1) - zn(1) - 0(a)(x2) r27,4(2) - - (1) IIean I.9s8 0(I) zn(l) 0(4')(x2) 102.9 0(3) r1 0.099 95(L2) 1,26(6) 36(4) (2) 0(4)-zn(l)-0(4') r10.6 T2 0.123 L2(9) 83(9) 79(r2) 0(1) - 0(4)(x2) 3.sr2(4) 109.5 r3 0.173 101(6) 37(8) 5s(7) 0(1) - 0(4')(x2) 3.064(4) 0(1) - 0(1') 2.709 (7 ) 0(4) TL 0.o92 74(22) 49(25) 45(32) 0(4) - 0(4') 3.179G) 0.105 114(34 ) 42 (32) Lr2(45) Mean 3.L73 r3"2 0.175 ls1 (s) 98(3) 62(4)

Tl"E zn(2) - Tettahed8on zr(2) - 0(2) 1.98s(2) 0(2) - zn(2) - 0(3) 99'9(2) za(2) - 0(3) 1.953(3) 0(2) - zn(2) - 0(3') Lo9'2(2) Zn(2) - 0(3') 1.949(3) o(2) - zn(2) - o(4) 112'3(1) Zn(l)Oa tetrahedra;(b) tetrahedraldouble chains, zn(2) - 0(4) 1'966(3) 0(3) - An(2) - 0(3') 119'6(1) Zn(2)Oo tetrahedra;and Meao 1.964 0(3) - zn(2) - 0(a) 111'4(1) made up of corner-sharing 0(3') - zn(2) - 0(4) 104.s(I) (c) two isolated trigonal-pyramidal arsenitegroups, 0 (2) - 0(3) 3.016(4) Mean 109'5 0(2) - o(4) 3.284(5) As(1)O3and As(2)O,. o (2) - 0(3') 3.210(4) 0(4) - 0(3) 3.098(4) 0(4) - 0(3') 3.237(4) (a) Tetrahedral edge-sharingdimer, IZnzOuf 0(3) - o(3,) 3.373(3) ') l,lean 3. 203 Two Zn( l )Ontetrahedra share the O( I )-O( I edge The A6(1)03 TtigorcL futmid across a mirror plane, forming a lZnrO.]'- dimer As(l) - 0(1) 1.753(s) 0(r) - As(l) - 0(3)(x2) 97'6(1) (Figs. I and 2). This dimer is apparentlyof a new As(l) - 0(3)(x2) L.172(3) 0(3) - As(l) - 0(3!) 100'0(1) Mean 2. 766 Mean 98. 4 type. Becauseof the edge-sharing,the Zn(l)On tet-

0(r) - 0(3)(x2) 2.652(5) rahedron(av. Zn-O distance1.958A) is highly dis- o(3) - o(3') 2,715(5) (2.7094)is much l4ean 2.613 torted;the sharededge, O(1)-O(1') shorter than the average tetrahedral edge distance lhe As(2)0, TrigoML P!?@'Ld angle(86.1") is As(2) - 0(2) I.772(4) o(2) - As(2) - 0(4)(x2) 95'2(I) (3.173A),and the O(1)-Zn(1)-O(l') ls(2) - 0(4)(x2) 1.771(3) 0(4) - As(2) - 0(4') 100'0(1) much smallerthan the averagetetrahedral angle. The l,tean 1.771 Mean 96.8 Zn(l)-Zn(|') distancewithin the dimer is 2.8974. 0(4) - 0(2)(x2) 2.616(s) 0(4) - o(4') 2.713(4) Although a similar edge-sharingtetrahedral silicate Mean 2.648 dimer would be very unlikely, a topologically com- Zn-Zn qrul Zn-As Distances Zn-j-Zn AngLes parable [BerOu]8 dimer has been found in epididy- zn(1) - zn(1r) 2.8974(9) zn(1) - 0(1) - zn(1') 93.9(2) mite, HNaBeSi3O8(Robinson and Fang, 1970). zt(r) - zn(2) 3.2990(7) zr(2) - O(2) - zn(2') 115.9(2) zn(2) - zr(2') 3.3s90(8) zn(2) - 0(3) - zr(2') 108.1(1) zt(2) - zt(2' ') 3.3690(8) zn(1) - 0(4) - zn(2) 11s.6(2) (b) Tetrahedral double chains, [ZnoOro]*- zn(1) - As(l) 3.4219(8) Zn-)-As Angles running parallel to the a An(l) - As(2) 3.3025(7) A tetrahedralsingle chain zn(2) - As(l) 3.2673(7) zn(l) - 0(1) - As(l) 132.5(2) axis is formed by Zn(2)-tetrahedrasharing the oxy- zn(2) - As(1r) 3.3640(8) zn(2) - 0(2) - As(2) 119.1(1) zn(2) - As(2) 3.2054(8) zn(2) - 0(3) - As(1) 129.L(2) gen corner, O(3). Two such single chains across a za(z) - As(2') 3.2429(8) za(2') - 0(3) - As(l) 122'8(2) zn(l) - 0(4) - As(2) L26.r(2) mirror plane share corners, to form double chains zn(2) - 0(4) - As(2) 118.0(2) (Figs. 2, 3 and 4a). In Liebau's (1972) terminology GHOSEET AL.: REINERITE

(c) The arsenitegroups Both the AsO, groups are trigonal pyramids with point symmetry m, deviating significantly from the highest possible point symmetry 3m. The average As-O bond length and the pyramidal edge (O-O) distancesare 1.769 and 2.661A respectively,and the average O-As-O angle is 97.6'. Other than the closestthree oxygens,no oxygen atoms approachthe relativelyunshielded As3+ ion within 3.5A.

(d) The three-dimensionalframework The backbone of the reinerite structure is the tet- rahedral double chain running parallel to the a axis. Such double chains are cross-linkedthrough Zn-tet- rahedral dimers by corner-sharing,giving rise to a second type of Zn-tetrahedral corrugated chain run- ning parallelto the c axis (Fig. 4b). Sucha framework is further strengthenedby pyramidal arsenitegroups sharing cornersof two adjacentdouble chainswith a corner of the Zn-tetrahedral dimer (Fig. 3). Each oxygen atom is being shared by two zinc and one arsenlcatoms.

Discussion

Configuration of the arsenite group The accurate configuration of the trigonal-pyra- midal As3+Oagroups has been determined in rela- tively few minerals. In trippkeite, CuAsrOn, the As-O distancesare: 1.89(X2), 1.69,{ (av. 1.82A), where the arsenite groups share corners to form chains (Zemann, l95l). In synadelphite,Mnn(OH), (H,O),(AsOr)(AsOo), (Moore, 1970), asbecasite, Ca.Ti(As,SiBeO,o),(Canillo et al. 1969),and in fin- nemanite, PbuCl(AsOr), (Gabrielson, 1956), the As-O distancewithin the isolatedarsenite groups are 1.76,l.'191, and l.8lA respectively.The av. As3+-O distance(1.769A) within the arsenitegroups in reiner- Fig. l. A partial view of the reineritestructure, showing the atom ite is significantly shorter than all those mentioned nomenclatureand the ellipsoidsof thermal vibration. above, except in synadelphite. It appears that the As3+-O bond length is highly variable. However, this is a Zweier-Doppelketteor a double chain with some of the structures mentioned above, when re- two-tetrahedral repeat, accounting for the 6.09A q fined by modern methods,may show much lessvaria- axis. Thesedouble chains are comparableto the am- tion in the As3+-O bond length. phibole-type silicate double chains. However, the Crystal double chains with the composition [ZnnO,o]in reiner- chemistry of the tetrahedral [ZnOof- ion; a ite are characterized by four-membered rings, as comparison with the crystal chemistry of silicates opposedto six-membered rings in the [SioO,,]double The facility of the [SiOn]a-ion to polymerize,giv- chainsof amphiboles. ing rise to chains,rings, sheets,and framework struc- The Zn(2)O^ tetrahedron (av. Zn-O distance tures, is well known. The tetrahedral[ZnOn]6 ion is 1.9644) shows considerableangular distortion, the emerging in a similar r6le. Thus, a corner-sharing O-Zn-O angle ranging from 99.9 to 119.6'. pyroxene-type[ZnO"] tetrahedral chain is found in GHOSEET AL,' REINERITE l 133

Fig. 2 A partial view of the reineritestructure down the b axis, showing the tetrahedraledge-sharing [ZnrOu] dimers and tetrahedral corner-sharing fZn nOrol double chatns.

Fis. 3 A view of the reinerite structure down the a axis; the fZnoOro]double chains are projected end on. n34 GHOSEET AL REINERITE

Canillo, E , G Giuseppetriand C Tadini ( 1969)The crystalstruc- [ure ofasbecasite Accad. Naz Lincei, Ser. 8.46. 457-467 Cromer, D. T and D Liberman (1970) Relativisticcalculation of anomalous scattering factors for phys X-rays "/. Chem. , 53, r89l-1898 - and J B Mann (1968)X-ray scatteringfactors computed from numerical Hartree-Fock wave function Acta Crystallogr , A24.32t-324 Finger, L. W. (1969) Determination of cation distributions by Ieast-squaresrefinement. of single crystal X-ray data Carnegie Inst Ilash Year Book,67, 216-217 Gabrielson, O. (1956) The crystal structure of finnemanite pb" Cl(AsO,), Ark Mineral Geol .2. l-8. Geier, G. H. and K Weber (1958)Reinerit, Zns(AsO3),, ein neues Mineral der Tsumeb Mine, Siidwestafrika. Neues Jahrb Min- eral Monatsh.160-167. Germain, G., P Main and M. M Woolfson (1971)The appli- cation of phase relationshipsto complex structures III. The optimum use of phase relationships Acta Crystallogr.,A2Z, 368-376. Ghose, S. and C Wan (1974)Structural chemistryof copper and zinc minerals:Part II Stereochemistryof copper (il) and iodine (V) in belfingerite,3Cu(lor), 2H,O Acta Crystaltogr, 830, 965-974. -, S R. Leo and C Wan (1974) Structural chemistry of copper and zinc minerals: Part I Veszelyjte,(Cu,Zn)ZnpOA Fig 4. (a) The [ZnnO,o]double chain in reinerite (b) The corru- (OH), 2HrO: a novel type of sheetstructure and crystal chem- gated letrahedralchain with four-tetrahedralrepeat in rernente. istry of copper-zinc substitution.Am. Mineral , 59. 573-5g1. Karle, J and I L. Karle (1966)The symbolic addition proceoure gerstmannite,(Mn,Mg)Mg(OH),[ZnSio.] (Moore fbr phase determination for centrosymmetric and non-cen_ and Araki, 1977).ThelZnoOrcf-double chain found trosymmetric crystals Acta Crystallogr , 21, 849-g59 in reineriterivals the [Si,O,,]-double chain in amphi- Liebau, F. (1972)Crystal chemistryof silicon ln H K. Wedepohl, boles; furthermore, the corrugated chain in reinerite Ed., Handbook o/ Geochemistry,II-3, l4-A-l-32. Springer-Ver- lag, Berlin. is similar to the corrugated silicate chains found in Moore, P. B (1970) Crystal chemistry of the basic manganese alamosite,Pb12Si12Oa6 (Boucher and peacor, l96g). arsenates:IV. Mixed arsenicvalences in the crystalstructure of and in stokesite,CarSnrSirOr, (Vorma, 1963).How- synadefphite.Am Mineral, 55, 2023-203j ever, the corrugated chain in reinerite is a Vierer- - and T Araki (1977) Gerstmannile, a new zinc silicate Einfachkette,whereas the silicate chains in alamo- mineral and a novel cubic close-packedoxide structure. lm Mineral .62. 5l-59. site and stokesite are Zwblfer-Eidachkette and Robinson, P D. and J. H Fang (1970) The crystal structure Se c hs e r- E infachk et e respectively. of t epididymite.Am Mineral , 55, l54l-1549. Vorma, A (1963)Crystal structureof stokesite,CaSnSisO, Acknowledgment 2H,O. Mineral Mag ,33,615. We greatly are indebted to Mr John S. White, Jr, of the Zemann, J (1951) Formel und Kristallstrukturdes Triookeits Smithsonian Institution for the donation of this rare mineral for Tschermaks Mineral Petrogr Mitt , 2, 417-422 our investigation References Boucher, M L. and D R. Peacor(1963) The crystal structureof Manuscript receiued,April 13, 1977, accepted alamosite PbSioi Z Kristallogr 126, 98-llI , Jbr publication, July 8, t977.