Comparison with Leadhillite

Mineralogical Magazine, August 1998, Vol. 62(4), pp. 451–459

Crystal structureof macphersonite

(Pb4SO4(CO3)2(OH)2):comparison withleadhillite

1 1,2,3 4,5 IAN M. STEELE , JOSEPH J. PLUTH AND ALEC LIVINGSTONE 1 Department of Geophysical Sciences, 2 Consortium for Advanced Radiation Sources, 3 Materials Research Science and Engineering Center, The University of Chicago, Chicago IL60637, USA 4 Department of Geology, The Royal Museum of Scotland, Chambers St., Edinburgh EH11JF, UK

ABSTRACT

Thecrystal structure of macphersonite (Pb 4SO4(CO3)2(OH)2, Pcab, a = 9.242(2), b =23.050(5), c = 10.383(2) AÊ )fromLeadhills, Scotland has been determined to an R =0.053.The structure has many featuresin common with its polymorph leadhillite including three distinct types of layers. Layer A includessulphate tetrahedra, Layer B iscomposed of Pb and OH, whileLayer C iscomposed of Pb and CO3 withtopology identical to that in cerussite. In both macphersonite and leadhillite these layers are stackedalong [010] as ...BABCCBABCC... Thedouble CC layeris almost identical in the two structuresand forms a structuralbackbone and occurs in other structures including hydrocerussite and plumbonacrite.The sulphate layer shows the greatest difference between the two structures and can be describedby a patternof up or down pointing tetrahedra. For macphersonite the sequence along [001] is...UDUDUD ...whilein leadhillite the sequence along [010] is ... UDDUUDDU... Thislatter sequence effectivelydoubles b relativeto the equivalent direction in macphersonite. Susannite, a third polymorph,may have yet another sequence of sulphates to give trigonal symmetry; by heating leadhillite,displacive movements of sulphate groups may occur with a conversionto susannite.

KEY WORDS: macphersonite,leadhillite, susannite, cerussite, hydrocerussite, carbonate, sulphate.

Introduction Macphersoniteis the rarest of the three poly- morphs,only two composite crystals being known MACPHERSONITE (Livingstoneand Sarp, 1984) is onseparat especimensfrom the Leadhil ls- trimorphouswith leadhillite and susannite with Wanlockheadorefield. Parallel oxidatio nof thecomposition Pb 4SO4(CO3)2(OH)2. All are otherprimary sulphides of Cu and Zn lead to foundin the classic Leadhills region of southwest mixedmetal species of carbonates,sulphates and Scotlandand represent a smallfraction of the hydroxides. some60 minerals identified from this region Previousstudies of the these trimorphs have (Temple,1956) .Fromprimary galena, oxidation establishedtheir compositional identity and close productsincludeanglesi teand cerussit eor relationshipsamong their unit cell geometries hydrocerussite.These oxidized products lead to (LivingstoneandSarp, 1984). They can be awealthof minerals which include sulphates, distinguishedby differen cesin their X-ray carbonates,hydroxides, or mixtures thereof which patterns,albeit subtle differences in the case of includethe trimorphou sgroupabove; other susanniteand leadhillite (Livingstone and Russell, phasesaregiveninTemple(1956). 1985),or by their infrared absorption spectra (Russell et al.,1984).Thepolymorphs can also be distinguishedby their thermal behaviour (A.L. ,

5 unpublisheddata). The structure of leadhillitewas Present address: 6St. Ronan ’sTerrace, Innerleithen, describedby Giuseppetti et al.(1990)in which a Peeblesshire EH44 6RB, Scotland doublelead carbonate layer, nearly identical to

# 1998The Mineralogical Society I. M. STEELE ETAL.

layersin cerussite, anchors a structurewhich (1984).Sufficientmaterial (NMS G1991-31-21) includesPbSO 4 and Pb(OH)2 layers.The dimen- wasavailable to selecta samplefor single crystal sionalsimila ritiesbetwee nleadhillitea nd studiesbut the common twinning made it difficult macphersoniteindicate that the latter has a toobtain a singlecrystal. Multiple crystals could similarstructure and our main objectives are to usuallybe recognized optically, but only after determinethe macphersonite structure and then to confirmationwith routine precession photographs comparewith leadhillite and possibly suggest wasa sample,free of twinning, obtained. variationsfor the susannite structure. Thesample selected for single crystal data Whilethese objectives are primarily crystal- collectionwas a cleavageplate with dimensions lographic,it should be pointed out that the lead giveninTa ble1.Pre cessionp hotographs carbonates,sulphatesand hydroxides play a confirmedthe space group as Pcab with a cell significantrole in thelead acid battery chemistry. of a = 9.24, b = 23.0, c = 10.4 AÊ ,consistentwith Structuralderivatives where sulphate or hydro- datareported by Livingstone and Sarp (1984). xidegroups replace Pb in either the tetragonal Diffractionswere sharp with no indication of (litharge)or orthorhombic (massicot) PbO struc- multiplec rystalsortwinn ing.The c rystal turescomprise intermediate lead sulphates in the (completedetails in Table 1) was mounted on productionof lead acid batteries (Steele et al., anautomated Picker-Kris el4-circle diffract- 1997;Steele and Pluth, 1998) .Detrimentalto lead ometer with b offset 18 from the f axis. acidbatteries is the formation of lead carbonate- Refinementusing 23 diffractions (17 < 2 y < hydroxidesincluding hydrocerussite and plumbo- 348: l = 0.71073 AÊ ),eachthe average of nacrite.The mechanism of formation of these automaticcentring of 8 equivalentsettings gave phasesis not well known, but their presence in thefinal cell parameters (Table 1) consistentwith batteryplates reduces acid permeability within the PbO2 networkand increases the resistivity of the electrolyte(Vinal, 1955). While these two phases TABLE 1.Experimental details and crystallographic commonlyoccur, one may expect other phases datafor macphersonite includinglead carbonate -sulphate-hydroxides, possiblymacphersonite and/ orleadhillite, may alsoform within lead acid batteries. Natural (A) Crystal-cell data occurrencesof lead silicate-carbonate -sulphate- a (AÊ ) 9.242(2) hydroxideshave been documented, e.g. kegelite b (AÊ ) 23.050(5) Ê (Dunn et al.,1990),mattheddleite (Livingstone et c (A) 10.383(2) Ê 3 al.,1987),and an unnamedphase (Cipriani et al., V (A ) 2211.9(8) Space group Pcab 1995),and given that silica within a leadacid Z 8 batteryis extremely detrimental, one can spec- Formula Pb4SO4(CO3)2(OH)2 ulatethat these or similar compounds form and ­ 3 Dcalc (g cm ) 6.480 effectivelypreven tnormale lectrochemical m (mm ­ 1) 60.96 reactions. Fromboth an academic and industrial point of (B) Intensity measurements view,the description of the lead compounds of Crystal size 80 6 55 6 25 mm carbonate,sulphate and hydroxide may prove Diffractometer Picker, Krisel control usefulfor interpreting both natural and synthetic Monochromator Graphite chemicalsystems. The natural occurrences of Radiation MoK minerals,such as described here, offer advantages Scan type o becauseproducts are available of sufficient size 2y range 3.5 ­ 55.0 Diffractions measured 10,206 foraccura tedo cumentationincontra stto Unique diffractions 2,556 industrialoccurrenc eswhich are notorious ly fine-grained. (C) Refinement of the structure

R 0.053 R = S(||Fo|-|Fc||)/S|Fo| Rw 0.121 Rw = Experimentaldetai ls andstructure solution 2 2 2 2 2 Ý [Sw(|F0|-|Fc|) /Sw|F0| ] Theoccurrence of macphersonite,its relationships Variable parameters 173 toothercoexisting lead phases, and its properties ‘Goodness of fit ’ (GOF) 1.1 havebeen described by Livingstone and Sarp

452 CRYSTAL STRUCTURE OFMACPHERSONITE

2 2 ­ 2 2 theprecession study. A totalof 10,206 intensities totalcounts) ], w = (sF) ,R(F) =0.053,R w(F ) werecollected with o stepscans, 0.02 8 steps, 1 =0.121,S =1.09;largest shift/ e.s.d.~0.002 for all sec/step,and a scanwidth 1.0 8 for a 2y range of parameters;maximum and minimum heights on 3.5­ 558.Mergingyielded 2,556 intensities (R int = finaldiffer ence-Fouriermapare+6. 4and 0.063),all of which were used in refinements: ­ 5.1 eAÊ ­ 3;computerprogra ms:local data datacollection range h + 12, k = 0 to 30, l + 13; reduction,SHELXTL TM.Finalatomic coordi- meanintensity variation of 3standarddiffractions natesand isotropic displacement parameters are = 6%.Ananalytical absorption correction was givenin Table 2, anisotropic displacement para- appliedto the data using the m valueand crystal metersin Table 3, and interatomic distances in dimensionsin Table 1. Systemati cabsences Table 4. indicatedspace group Pcab consistentwith the precessionstudy. The initial model was derived fromthedirectmethodsprogrammein Discussionof structure SHELXTLTM (Trademarkof Siemens Energy Themacphersonite structure can be best repre- andAutomation,Inc.,Analytical sentedas a sequenceof three types of layers Instrumentation,Madison, WI, USA). AllPb stackedalong [010] .LayerA iscomposed of atomswere included in a leastsquares refinement sulphatetetrahedra, Layer B ofleadand OH, and usinganisotropic temperature factors, and the S, LayerC oflead and carbonate. The stacking O,andC positionswere located in subsequent sequenceis illustratedwith a projectionparallel to difference-Fouriermaps and included in the [100]inFig. 1 andcanb edescribedas refinement. ...BABCCBABCC... stacking.These same layers Inthe final model, 173 variables were refined: willbe shown later to occur in the leadhillite scalefactor, extinction parameter, positions for 19 structurein which the same stacking sequence atoms,and anisotrop icdisplaceme ntfactors. occurs.Each layer is illustrated in plan view in Neutralscatteri ngfactors found internal to Fig. 2a, b and c. SHELXTL wereused. The final least-squares LayerA, composedof sulphate groups is 2 2 refinementminimized all F s with sF computed shownin Fig. 2 a andit is apparent that the from sI,thesquare root of [totalcounts + (2 % of sulphatesare arranged on ahexagonalnet with an

TABLE 2.Positional and isotropic displacement parameters for macphersonite

Atom x y z *Ueq

Pb (1) 0.06550(5) 0.44671(2) 0.87282(5) 0.0166(2) Pb (2) 0.39976(6) 0.54944(2) 0.88805(5) 0.0164(2) Pb (3) 0.13688(6) 0.83923(2) 0.91390(5) 0.0199(2) Pb (4) 0.53367(6) 0.66070(2) 0.65959(6) 0.0238(2) S 0.2642(4) 0.7562(1) 0.6177(3) 0.0175(9) O(1) 0.100(1) 0.3529(4) 0.916(1) 0.024(3) O(2) 0.388(1) 0.5654(4) 0.6361(9) 0.016(3) O(3) 0.112(1) 0.4219(4) 0.6375(8) 0.019(3) O(4) 0.176(1) 0.9255(4) 0.739(1) 0.023(3) O(5) 0.438(1) 0.6453(4) 0.870(1) 0.023(3) O(6) 0.180(1) 0.5656(4) 0.741(1) 0.018(3) O (7) ­ 0.187(1) 0.4233(4) 0.977(1) 0.022(3) O(8) 0.734(1) 0.6948(4) 0.851(1) 0.030(3) O(9) 0.416(1) 0.7648(5) 0.649(1) 0.037(4) O(10) 0.682(1) 0.5632(4) 0.974(1) 0.017(3) O(11) 0.238(1) 0.7650(4) 0.478(1) 0.028(3) O(12) 0.172(2) 0.7949(6) 0.691(1) 0.045(4) C(1) 0.248(1) 0.5648(5) 0.634(1) 0.011(3) C(2) 0.251(1) 0.9237(6) 0.633(1) 0.014(3)

3 3 *Ueq is defined as 1/3 i 1 j 1 Uijai aj ai aj ˆ ˆ … † P P 453 I. M. STEELE ETAL.

TABLE 3.Anisotropic displacement parameters for macphersonite

Atom U11 U22 U33 U23 U13 U12

Pb(1) 0.0111(3) 0.0179(3) 0.0208(3) ­ 0.0002(2) ­ 0.0002(2) 0.0006(2) Pb(2) 0.0122(3) 0.0182(3) 0.0187(3) 0.0009(2) ­ 0.0005(2) 0.0003(2) Pb(3) 0.0174(3) 0.0180(3) 0.0242(3) ­ 0.0011(2) ­ 0.0034(2) ­ 0.0027(2) Pb(4) 0.0188(3) 0.0222(3) 0.0303(3) 0.0027(2) 0.0024(2) ­ 0.0030(2) S 0.011(2) 0.017(2) 0.025(2) ­ 0.001(1) ­ 0.002(1) ­ 0.001(1) O (1) 0.014(5) 0.014(4) 0.044(7) ­ 0.001(4) ­ 0.006(5) 0.007(4) O (2) 0.003(4) 0.026(5) 0.020(5) ­ 0.002(4) 0.001(3) 0.001(4) O (3) 0.012(4) 0.037(5) 0.006(4) 0.000(4) 0.001(3) ­ 0.003(4) O (4) 0.009(5) 0.040(5) 0.020(5) ­ 0.004(4) 0.002(4) 0.003(4) O (5) 0.020(5) 0.015(5) 0.033(6) 0.001(4) 0.004(5) 0.002(4) O (6) 0.011(4) 0.021(4) 0.022(5) 0.009(4) 0.004(4) 0.003(4) O (7) 0.010(4) 0.031(5) 0.024(5) ­ 0.001(4) ­ 0.005(4) 0.003(4) O (8) 0.033(6) 0.023(5) 0.036(6) ­ 0.009(5) 0.002(5) ­ 0.010(5) O (9) 0.019(6) 0.033(6) 0.059(8) 0.011(6) ­ 0.010(6) ­ 0.014(5) O(10) 0.014(5) 0.017(4) 0.020(5) ­ 0.002(4) 0.008(4) 0.001(4) O(11) 0.035(6) 0.020(5) 0.028(6) 0.001(4) ­ 0.001(5) 0.001(4) O(12) 0.059(9) 0.052(7) 0.023(6) ­ 0.012(5) ­ 0.006(6) 0.026(7) C (1) 0.011(5) 0.001(4) 0.021(6) 0.000(4) 0.002(5) 0.000(4) C (2) 0.008(5) 0.014(6) 0.019(6) 0.006(5) 0.003(5) ­ 0.003(4)

alternationof up or down pointing tetrahedra approximatelyequidistant from three sulphate along[001 ].LayerA issandwichedbetween two groupsof layer A. Theother half of the possible B,orPb-OH layers,one of which is shown in positionsin layer B, whichare again approxi- Fig. 2b.Inany B layer,the Pb atoms form an matelyequidistan tfrom3 layerA sulphate approximatehexagonal array with each Pb atom groups,are occupied by OH groupsalso in an

TABLE 4.Bond lengths (A Ê )formacphersonite (Pb 4SO4(CO3)2(OH)2)

Pb (1) ­ O(1) 2.232(9) Pb (2) ­ O(5) 2.245(10) Pb (3) ­ O(1) 2.452(10) ­ O(3) 2.545(9) ­ O(7) 2.495(10) ­ O(12) 2.549(11) ­ O(4) 2.563(10) ­ O(6) 2.570(10) ­ O(10) 2.566(9) ­ O(7) 2.628(10) ­ O(2) 2.644(9) ­ O(11) 2.661(10) ­ O(2) 2.781(9) ­ O(3) 2.675(9) ­ O(4) 2.715(10) ­ O(4) 2.807(10) ­ O(10) 2.779(10) ­ O(8) 2.721(12) ­ O(10) 2.829(10) ­ O(6) 2.937(10) ­ O(9) 2.747(11) ­ O(10) 3.060(9) ­ O(5) 2.922(10) ­ O(3) 3.033(10)

Pb (4) ­ O(5) 2.385(10) C (1) ­ O(10) 1.27(2) S ­ O(12) 1.449(12) ­ O(2) 2.587(9) ­ O(6) 1.28(2) ­ O(9) 1.450(11) ­ O(9) 2.637(12) ­ O(2) 1.30(2) ­ O(8) 1.480(10) ­ O(6) 2.772(9) ­ O(11) 1.488(11) ­ O(8) 2.826(12) ­ O(1) 2.831(12) C (2) ­ O(3) 1.27(2) ­ O(8) 2.879(11) ­ O(7) 1.29(2) ­ O(11) 2.922(11) ­ O(4) 1.30(2) ­ O(7) 3.059(10)

454 CRYSTAL STRUCTURE OFMACPHERSONITE

FIG.1. Projection of Pb, Cand SO 4 parallel to [100]. Clearly shown are three types of layers: A–SO 4 groups; B–Pb and OH;and C–Pb and C.The sequence of layer stacking is ....CCBABCCBA....

hexagonalarray. In the B layeron the opposite sideof layer A, Pband OH havethe same configurationbut with Pb and OH interchanged. LayerC isshown in Fig. 2 c and can be consideredas interpenetrating hexagonal nets of Pb and CO3 groups.This geometry is virtually identicalto that found in cerussite, PbCO 3 (Sahl, 1974).Thetwo C Layerstogether are shown in Fig.3 andbasically reproduce a slabof the cerussitestructure and might be considered as an ‘anchor unit’ becausethis unit is also found in boththe hydrocerussite (Steele et al., 1998) and

plumbonacritestructures (Cowley, 1955; Olby, FIG. 2. (a) Layer A, (b)Layer B,and ( c)Layer Cin plan 1966). view by projection parallel to [010].In (a) the SO 4 Tobetter understand the crystal chemistry and groups are in an hexagonal net as outlined by the dashed physicalproperties of macphersonite it is helpful lines. Likewise in (b) the Pb atoms, Pb3 and Pb4, like toconsider the charges of theA, BandC layers. the SO4 groups in (a), lie in adistorted hexagonal net TheA layercontains SO 4 groupswith a chargeof shown by the dashed lines with each Pbcentred among + ­ 2.Two Blayerscontaining Pb(OH) sandwich three SO4 groups in the adjacent Alayer. Nearly theA layerand together produce a neutralslab. coplanar with the Pb are OHgroups, O1 and O5, also Two Clayersof PbCO 3,alsoneutral, bridge two centred among three SO 4 units.In (c) the hexagonal net B-A-B slabs.The weak connection between these repeats for both Pb and CO 3 as indicated by dashed slabsleads to the perfect {010} cleavage. lines.

455 I. M. STEELE ETAL.

andPb2 in macphersonit eandPb1 through Pb4 inleadhillite ),aresurrounded by six oxygens from CO3 groupsin the plane of Layer C. In theseviews, each Pb has an OH directlybelow andthree oxygens above but only those with Pb- Olessthan 3.20 A Ê areshown. Thus each Pb in LayerC hasnearly identi calcoordi nation geometry.Leadhillite shows marginally longer C-Obondswithin the C Layer(average = 1.314 AÊ ,range= 1.27to 1. 36A Ê ) than in macphersonite(average = 1.284A Ê , range = 1.27to 1. 30A Ê )orcerussite (average = 1.27A Ê ). Likewise,the Pb-O bonds in theplane of LayerC inleadhillite are on average (24 Pb-O distances average2. 672A Ê )almostidentical to those in macphersonite(12 Pb -Odistancesaverag e 2.688 AÊ )andcerussite(6 Pb -Odistances average2.713 A Ê ).All Pb-O bond lengths for Pb-OH whichrange from 2. 20to 2. 27A Ê in leadhilliteare similar to thosein macphersonit e (2.23to 2. 25A Ê ). Detailsof Layer B inboth macphersonite and leadhilliteare illustrated in Fig. 5 (top).For macphersonitethe environment for both Pb3 and Pb4is similar with 9-fold coordination: three oxygensof three CO 3 groups,four oxygens from sulphategroups,and two OH groups.For

FIG.3. The double C-Clayer in macphersonite leadhillitethe situation is more complex with illustrated both in plan view and in profile is nearly Pb7and Pb8 having the same number and type of identical to cerussite, PbCO 3 (Sahl, 1970).Numbers in coordinatingoxygen sasin macphe rsonite; upper half of [010] projection represent fractional however,Pb6 is nine coordinated with three heights while numbers in lower half represent atom oxygensfrom three CO 3 groups,five from identifiers from Table 2. sulphategroups and one OH whilePb5 is eight coordinatedwith three oxygens from three CO 3 groups,two from sulphate groups, and three OH . Thesecoordinations are based on Pb-O distances Comparisonwith leadhi lliteand cerussite lessthan 3.20 A Ê ;greatercoordination is present if longerbond lengths are considered. Theleadhillite cell dimensions ( a = 9.11, b = Acomparisonof LayerA isillustratedin Fig.6 20.82, c = 11.59 AÊ , b = 90.468)showa close andpossibly shows the most significant differ- similarityto those of macphersonitewith alead & encesbetween macphersonite and leadhillite. For Ýbmac, blead & 2cmac, clead & amac, and blead & eachphase the sulphate groups can be considered 908 (Giuseppetti et al.,1990).The leadhillite toeither point up (U)ordown(D) .Forleadhillite structureis schematically shown in Fig. 4 andcan arowof sulphate tetrahedra parallel to [010] becompared directly with Fig. 1. Other than the showsthe sequence ... UDDUUDDU... whereasin reorientationand changes in cell dimensions, the macphersonitethe sequenc ealong[001 ]is samelayer sequence ... BABCCBABCC... is ...UDUDUDUD... Thisdoubling of the sulphate apparent.The double Pb-CO 3 units(Layers CC) repeatappears to be the major factor causing a aretopologically equivalent to those of macpher- doublingof the cell length in leadhillite with the soniteand cerussite (Sahl, 1974) . additionaleffect of creatingdifferent coordination Figure5 (bottom)shows a comparisonof the geometriesabout the Pb atoms of Layer B (see coordinationwithinthe carbonate layer (Layer previousparagraph) in contrast to macphersonite C)formacphersoni teand leadhillite looking wherethe coordination geometries for all Pb in perpendicularto this layer. All Pb atoms (Pb1 LayerB issimilar.

456 CRYSTAL STRUCTURE OFMACPHERSONITE

FIG.4. The layer structure of leadhillite which can be compared with macphersonite of Fig. 1. This view clearly shows the ....CCBABCCBA....layer sequence, identical to macphersonite.

Discussion stronghexagonal relationship sinall layers of boththese phases and this was also recognized Theabove comparison of these two polymorphs byGiuseppetti et al.(1990).A majorviolation of hasshown that they are composed of three thetrigonal geometry is the orientation of the similarunits. The double carbonate sheet is sulphategroups, not their position. To attain nearlyidentical in the two structures and forms trigonalsymmetry for either macphersoni teor thebackbone. This similarity was also recog- leadhillitea reorientationof sulphate tetrahedra nizedin the infrared spectra. The sulphate layer mustbe made. Heating leadhillite to about80 8C clearlydiffers between the two and is thereason asdemonstrated by several studies (Mrose and forcell doublin g.The differe ncesbetween Christian,1 969;Giuseppetti et al., 1990; leadhilliteand heated leadhillite have also been Milodowskiand Morgan, 1984) gives subtle attributedto therelative relations of thesulphate changesin the diffraction pattern and a trigonal tetrahedrawhile the carbonate backbone unit phasethought to be susannite. This heating may maintainswith near-consta ntgeometry. While resultin a minordisplacemen tofthesulphates to thestructur eofsusanni te,the trimorph of givethe higher symmetry also recognized in the leadhilliteand macpher sonitehas not been infraredabsorption. Macphersoni te,on the other determined,the reported hexagonal cell with a hand,would be more difficult to transform to = 9.072 and c = 11.539 AÊ (Livingstoneand susannitedue to its doubled b and the two Russell,1985) suggests very strong relationship s differentsulphate layers in this larger cell. We bothdimensionall yandgeometricall ytoboth proposetonextinvestigateth esusannite leadhilliteand macphersonit e.We havenoted the structure.

457 I. M. STEELE ETAL.

FIG.6. Comparison of layer Afor macphersonite and leadhillite. An important difference is the sequence of orientations of these tetrahedra. In macphersonite the up-down sequence along [001] is ..UDUD..while in leadhillite the sequence is ..UDDUUDD..which effectively doubles b.

Acknowledgements

I.M.S.appreciatesfinancial support from NASA NAGW-3416;J. J.P.thanks MRSEC (grantNSF- DMR-00379)and CARS (grantsDOE FG02- 94ER14466and NSF EAR-9317772)both at the Universityof Chicago for financial support. We appreciatethe efforts of J.V. Smith to locate this materialand recognize through his structural FIG.5. Coordination details within layers Band Cof compilationsthat the structure was unpublished. leadhillite and macphersonite. Within layer Bof macphersonite, Pb3 and Pb4 have similar coordination References with three oxygens (unfilled symbols) shared with CO 3 groups, four oxygens shared with SO 4 groups, and two Cipriani, C., Corazza, M. and Pratesi, G.(1995) Anew OH.For leadhillite, Pb7 and Pb8 have coordination as in lead silicate sulfate hydroxide from Val Fucinaia, macphersonite. Pb6 and Pb7 coordinate to three oxygens Tuscany, Italy. Per. Mineral ., 64, 309­ 13. of CO groups, but Pb6 includes five oxygens from 3 Cowley, J.M. (1955) Electron-diffraction study of the sulphates and one OHwhile Pb5 includes 2oxygens structure of basic lead carbonate, 2PbCO .Pb(OH) . from sulphates and 3OH.Only Pb-O bonds of 3.20 A Ê 3 2 Acta. Crystallogr ., 9, 391 ­ 6. or less are considered. For layer Cof macphersonite, each Pb is surrounded by three nearly coplanar Dunn, P.J., Braithwaite, R.S.W., Roberts, A.C.and carbonate groups, in addition to an OHdirectly below Ramik, R.A.(1990) Kegelite from Tsumeb, and oxygens (unfilled symbols) above only shown if Pb- Namibia: Aredefinition. Amer. Mineral ., 75, 702­ 4. Oless than 3.20 A Ê .The numbers on the atoms represent Giuseppetti, G., Mazzi, F.and Tadini, C.(1990) The sequential assignment for each atom type for leadhillite crystal structure of leadhillite: Pb 4(SO4)(CO3)2 (Giuseppetti et al.,1990), or from the present Table 2for (OH)2. Neues Jahrb. Mineral., Mh ., 255­ 68. macphersonite. Views are shown perpendicular to the Livingstone, A.and Russell, J.D. (1985) X-ray powder layers. data for susannite and its distinction from leadhillite. Mineral.Mag ., 49, 759 ­ 61.

458 CRYSTAL STRUCTURE OFMACPHERSONITE

Livingstone, A. and Sarp, H. (1984) Macphersonite, a Cerussit, PbCO 3. Zeit. Kristallogr ., 139, 215­ 22. new mineral from Leadhills, Scotland, and Saint- Steele, I.M. and Pluth, J.J. (1998) Crystal structure of Prix, France –apolymorph of leadhillite and tetrabasic lead sulfate (4PbO.PbSO 4): an inter- susannite. Mineral. Mag ., 48, 277 ­ 82. mediate phase in the production of lead acid Livingstone, A., Ryback, G., Fejer, E.E.and Stanley, batteries. J. Electrochem. Soc ., 145, 528­ 33. C.J. (1987) Mattheddleite, anew mineral of the Steele, I.M., Pluth, J.J. and Richardson, J.W., Jr. (1997) apatite group from Leadhills, Strathclyde Region. Crystalstructureoftribasiclead sulfate Scott. J.Geol ., 23, 1­ 8. (3PbO.PbSO4.H2O)by X-rays and neutrons: an Mrose, M.E.and Christian, R.P.(1969) The leadhillite- intermediate phase in the production of lead acid susannite relation (abstract). Canad.Mineral ., 10, batteries. J. Solid State Chemistry , 132, 173­ 81. 141. Steele, I.M., Pluth, J.J. and Richardson, J.W., Jr. (1998) Milodowski, A.E.and Morgan, D.J. (1984) Thermal Occurrence and crystal structure of hydrocerussite reactions of leadhillite Pb 4SO4(CO3)2(OH)2. Clay from Leadhills, Scotland. In preparation. Minerals, 19, 825­ 41. Temple, A.K.(1956) The Leadhills-Wanlockhead lead Olby, J.K. (1966) The basic lead carbonates. J. Inorg. and zinc deposits. Trans. Roy. Soc. Edin ., 63, Nucl. Chem., 28, 2507 ­ 12. 85 ­ 113. Russell, J.D., Fraser, A.R.and Livingstone, A.(1984) Vinal, G.W. (1955) Storage Batteries (4th ed.).Wiley, The infrared absorption spectra of the three 446 pp. polymorphs of Pb 4SO4(CO3)2(OH)2 (leadhillite, susannite, and macphersonite) . Mineral. Mag ., 48, 295 ­ 7. [Manuscript received 2September 1997: Sahl, K. (1974) Verfeinerung der Kristallstruktur von revised 23 December 1997 ]

459