61.
Tlrc Catwdian M ineral ogi st Vol. 34, pp.6lJ2 (1996)
CLINOAilACAMITE,A NEW POLYMORPHOF Gur(OHl3Cl, AND ITS RELAflONSHIPTO PARATACAMITEAND 'ANARAKITE"*
JOHNL. JAMBOR Department of Earth Sciences, University of Waterlao, Waterloo, Ontario N2L 3GI
JOHNE. DUTRZAC CANMET,Deparnnent of Naaral ResourcesCananq 555 Booth Street, Ottawa, Ontaria KIA OGj
ANDREW C. ROBERTS GeologicalSurvey of Cananq601 Booth Street, Otawa" Owaria KIA 088
JOELD. GRICE ResearchDivisiou CatadianMuseurn of Naure, Ottatva,Ontaria KIP 6P4
JANT. SZYMA(SKI CANMET,Depamnent of NaturalResources Canad4 555 Booth Street, Ottawo" Ontario KIA 0GI
ABSTRA T
The new mineral clinoatacamiteis a polmorph of Cu2(OII)3C| othen are botallackite (monoclinic), atacamite(ortho- rhornbic),an{ possiblyparatacamite (rhombohedral). Clinoatacanite is monoclinic, spacegroup P21ln,a 6.157(2),b 6.814Q), c 9.104(5) A, p 99.65(4)", which is transformableto a pseudorhombohedralcell approximating that of paxatacamite. Clinoatacamitehas been found in specimensfrom severallocalities, aad coexistswith paratacamitein the holotype specimenof p,aralacamite.The two minerals are not readily distinguishedexcept by optical and X-ray methods:paratacamite is uniaxial negative, whereasclinoatacamite is biaxht negative, 2V@75(5f . Strongestlines of the X-ray powder paltern of clino- aracamireld n A(D@k[)]are 5.47(100)(T0l,0Ll),2.887(40X121J03),2.767(60)81.1),2.742Q0)(0r3,202),2.266(@)Q20), 2.243(50)(004),and L.7M(5Q82a,040). Clinoatacamiteis readily synthesizedand a seriesof experimentswas conductedto promotethe uptakeof Zn and duplicatethe formula of the dubiousmineral "anarakite" (CuZn)2(OI{)3C1.Generally, products with more than about6 mol%o"7iproved to be hexagonal,i.e., nrcranpaatacamite, as did specimensof "anarakite"fron fhe type locality. Holotype paratacamitecontains 2-3 wtVo Zn, andit seemsthat r€placementof Cu by small amountsof another cation, such as Ni or Zn, is eitler favorable or essentialto stabilize the rhombohedral(pantacamit€) structure.The Powder Diffraction File standardfor paratacamite(25-l4n) is that of clinoatacamiterather than paratacamite.
Keyword*: clinoatacamite,new mineral species,paratacamite, anarakite, Cu2(OlI)3Cl polymorphs, synthesis,Zn-Ni{o substitutions,X-ray data-
SoM:rteRs
l,a nouvelleespbce mindrale clinoatacamire est un polymorphede Cu2(O[I)3CI,les autres6tant botallackite (monoclinique), atacamite(orthorhombique), et possiblementparatacarrite (rhombo6drique). Ia clinoatacamiteest monoclinique, groupe spatial P21ln,a 6.157Q), b 6.814Q), c 9.LM(5) A, p 99.65(4f, une maille qui est transforrnableen une auhe,pseudorhombo6drique, approximativemeirtcelle de la paratacamite.Nous avons trouvd la clinoatacamitei plusieurs endroits; elle coexiste avec paratacamitedans le sp&imen holotype de cette dernibre.Les deux min6rauxne sont pas facilementdiff6renciables, sauf par m6thodesoptiques et par ditfraction X: la paratacamiteest uniaxe n6gative,tandis que la clinoatacamiteest biaxe n6gative, 2[re756)z.trlraai les plus intensesduilichd de diffraction X de la clinoatacami?e,mdthode des poudres ld ea A\D(hlAl sonc 5.47(100)(T01,011),2.887(n)621,,T03), 2.767(60)8rD, 2.7MQ0)(0r3,202), 2.266(6q2n), 2.243(s0)(0M), et 1,3M(50)824,A4q. I1 est facile de synthetiserla clinoatacamite;nous avons effectu6 une sdrie de slnthbsespour 6tudier ', f incorporation du 7n et 6valuer la formule d'une espbcedont le statut est encore douteux, "l'anarakite de stoechiom6trie
* GeologicalSurvey of Canadaconnibution number21695. 62 TIm cANADTANMrNERALocrsr
(Culn)2(OFI)3C1.En g6n6ral,les produits de synthbsecontenant plu s de 6Vode 7n @asemolaire) sont hexagonaux,c'est-l-dire une paratacamitrszincifbre, tout commeles echantillons"d'anarakite" provenant de la localit6 type. La paratacamiteholotypique contient de 2 d,3%o(poids) de Zn, etil sembleque I'incorporarionde petites quantit6sd'un autre cation, commeNi ou Zn, soit favorableou essentielled la stabilisationde la strucftre rhombo€driquede la paratacamite.L€ spectrede dii&action X que l'on attribuei la paratacamitedans le fichier de specnasde diffraction, m6thodedes poudres (fiche 25-I4X) est en fait celui de la clinoatacamite. (Traduit par la Rddaction)
Mots-cl6s: clinoatacamite,nouvelle eslDce min6rale, pamtacamite,'anarakite', polymorphes de Cu2(OI{)3C1,synthbse, substitutionsZn-Ni-Co. donn6esde diffraction X.
ItnonucnoN Pnnnrncal\ffre
Cu2(OII)3CI has been consideredto exist as the Paratacamiteis rhombohedral.The unit cell has trimorphous minerals atacamite (orthorhombic), been determinedby single-crystalX-ray methodsby paratacamite(rhombohedral), and botallackite (mono- Frondel(1950), Fleet (1975),and hing et al. (1987). slinis), ths crystal stuctures of which have been Fleet's (1975) crystal-structurestudy showedthat tle described by Wells (1949), Fleet (1975), and mineral has a pronouncedsubcell with a' = el2, c' = c, Hawthome (1985), respectively.In addition to these apparent space-group Rim. T\e superstructure is well-characterizedminernls, a syntheticphase assigned developedby an orderedarangement of the substruc- the sameformula was describedby Oswald& Guenter ture, and resultsin thq spacegroup R3 for the full cell (1971)as paratacamite, and is recordedas paratacamite with a 13.65,c 14.04A. The supersffucturedimensions in the Powder Diffraction File @DF 25-1427): thts were also obtainedby Frondel (1950) and Yrng et al. syntheticphase, however, has a monoclinic cell rather (1e87). than the rhombohedralcell ascribedto paratacamiteby Frondel(1950) and Fleet (1975). ooANAPrlI TABLB 1. X.RAY POWDBR,DATA FOR ANARAKIIts, ZNCI.AN PARATACAMIIE, AND CLINOATACAMIIE Anaraldte Znrian Pararamile Climatac{rfoe (Adlb&Oa€m.m 192) (thir sfidyf (ftis studyf ,t*I L d* il^' l{d ,d d* de hkl td*d* 65 5.476 s.&3 2.N 100 5.4 5.45 101 Lffi 5.A s.ql Ior,otr <5 5.O3 15 4.697 4.&2 W2 N 4.69 4.6E 0G 30 4.68 4.6E 101 5 4.52 4.52 012 <5 4.y 4.53 110 10 3.42s 3.$0 ttr L5 3.424 3.416 110 n 3,M 3.M,3.&7 t2,gm <5 3.019 3.019 104 m 2.fir 2.8W 220 n 2.8% 2.95 g)l & 2.EC7 2.W22.W2 L?L,',O3 1@ 2.755 2.759 gn 75 2.759 2.759 Ll3 @ 2.767 z.nl 11 _ 15 2.139 2.741 M n 2.726 2.7?.6 2V2 7O 2.7A 2.739,2.736 0132s) r0 2.713' 2.714 92,, t0 2.U2 2.W 1r4 LO 2.U3 2.W W 20 2.339' 2.339 82 70 2.253 2.?6 222 6 2.263 2.262 gU @ 2.26t 2.26 nO 50 2.243t 22A q04 l0 2.215 2.215 4n <5 2,210 2.2@ 211 5 2.2AE 2.2W 2-Lr 10 2.M2 2.W N2 10 2.035 2.87 245 5 2.U5t 2.U9 301 10 2.V15 2.Br Lt4 t0 2.927t 2.V27 123 <5 1.9301.931 116 1.940 310 ls t.w r,w2 n4 10 1.901 1.900 lW 5 1.907$1.S 301 10 1.895t 1.894 2_13 m Lw 1.828 6m 25 l.El7 1.817 033 20 1.817* 1.81E 231- 20 1.817 1.819 l0 1.807 1.809,1.806033,10s <5 1.751 1.749 rE 1.74 Ztr 30 1.708 1.708 040 35 1.708 1.70E 22JJ 50 1.704 1.105,1.7A nA,W <5 1.661l.@ 527 <5 1.64 l.@ 321 s r.630 1.630131 s t.626 1.62t 223_ <5 1.6011.& 2n 1.@1,r.@ l4L,!14 10 1.514 1.515 w2 7 1.509 1.509 208 s 1.51681.518,1.517 M,!n l0 1.50411.503,1.501 nA, Ll 15 1.4!16 043 L0 1.494 1.493 217 10 L.Nl 1Af,9,1.M A3,L% <5 1.4711.471 &1 s 1.471 1.4i11,1.467305,143 5 1.47 1.44? M2 5 l.us 1.447,1.46 Ul,Uz 5 1.420 1.419 !!9 10 1.384 6n $ 1.3E0 1.380 226 10 1.387* 1.386 42 5 t.m* Lm 242- ro t.3o 1.31t3M l0 1.368 r.370,1.?68 92j,M 5 1.350 1.351 321 5 1.35641.357 w <5 L.% l.w,L.y1 23/'051 <5 1.3111.308 045 rc r.no L269 0.2.10 L0 L.ny l.7ll 4n s 1.2tr r.26r.1.2ffi M,0r7 rc 1.A4 Lz}s 143 14& vahH added!o the data of Adib & oemsm, using tleb mo@lhis sell a 11.901, b 6.830, c Lg'162 L, B 112.8f. lZincisr Darataconit€roult obtalnedftom U4.54-lm Gadolff fln (Co nilhrim); idered vth hexrgoDalcel 4 6,592,16.832.'c L4.U2L4.u2 AtorAfor cotrqcotrct ndiadon OA 1.?8m1.78S A). SpctomS!€chrn fromfton Kattrrll Ka8Ka6 mhe' ler11klerlak P!ods,e' Irao Refinrmr|ltbas€dm2?dffiacdorlin€sb(fwe€,!S.4z.uALfMAtotwhic,hn'mbigl$ushdedngwas porslble. ldltnosla€snite ftom Chlquic€nar8, Cbile (M3217O; U4.54-m Deby&Sc&frtet pad€rq Cofor' hdex€d sth 4 6.157, b 6.814, c 9.10/1L 0 S9.Of. Diftadiotr lin6 wth an asledsk w€fe ured for the rmtt-cel rcfiD€mfd. Lire at 5.03 is assmed to be &e to alacamtle. showed no broadening or multiple-line diffraction refined to a 6.832,c 14.042A 6alte 1). Although the effects from Cu-Zn variation in a bulk sample.Two precession photographs showed no evidence of inferencesemerged from these results: (a) what we the strong supercell that is typically present in consideredto be the "anarakite-type"X-ray powder paratacamite,i,e., a = 2a', a 90-hour cone-a)ds pattempersists at relatively low Zn contents(ess than photographatong [100] confirmed the presenceofthe half that reported in the original paper), and (b) the supercell. The weaknessof relections attributed to differencesin our powder patternsof ooanarakiteo'and the supercell suggeststhat the ordered arrangement synthetic "paratacamite"@DF 23-947, 25-L42il) are of the substructuremay be affectedby the substitution not the result of progessive shifts in diffraction lines, of Zn for Cu: nevertheless"the unit cell of the Anarak suchas rnay occur in a solid-solutionseries. mineral is clearly that of a zincian rhombohedral Single-crystalX-ray study of a minute fragment of paratacamiterather than that of the monoclinic mineml ooanarakite'', the Pinch mounted about c*, Eave a describedby Adib & Ottemann(L972). hexagonal cell with cell dimensions subsequently As was statedabove, the X-ray powder datafor our 64 TABLB2 COMPARISONOF TIIE UNITCELIS OFAI.{AMK[BA}.ID reactor to initiate the precipitation reaction.When all SYNTIIETICOh(OlUCl the NaOH solution had been added,the resulting hot (Grzrxo.rl3cl Gr{oIUcl st/d€tic. slurry was filtered; the precipitate was washedwith @M{lr}' syMC ffird3 water and was dried at 110'C prior to chemical a(4) n.eol u.&3 ll.a analysisand mineralogical study. Test variablesfor the ,(4) 6.ao 6.W 5.W, synthesesincluded the concentrationsof the various c(A) 10.162 6.166 10.103 p. 11257 130.62 nztv, metal ions, the solutionpH, the ratio of NaOtI/il+, the methodand rate ofreagent addition, and the effect of lAdib& OuemamQgrZZ), Ar8als It@ nifrateversus chloride an:ions. qwld&GEtrs09l) eam*ers of tle Osrald& Aleder(197t) cell atec wing dD tird(frdion For chemical amlysis, the dried sampleswere dis- ofKEsls & Pertlk0983) solvedin 1:1 HNO3 and were diluted to an appropriate volume. Concenfrationsof Cu, Zn, Ni, and Co were determinedby atomic absorption spechoscopywith matrix-matchedstandards. Chlorine was determined by zincian pmatacamiteand that of o'anarakite"(Adib & high-pressure liquid chromatography and by ion- Ottemann1972) arein fairly good agreemen!and the selective elecftodes,with the two methods yielding several additional weaker lines recorded here for comparableresults. the pattem of zincian paratacamite(Iable 1) can be X-ray-diffraction data for the synthetic CvZn satisfactorilyindexed with the monoclinic cell of Adib productswere collectedmainly with a Rigaku rotating- & Ottemam. The major difference betweenthe two anodediffractometer operated at 55 kV, 180mA, using pattemsis the appearanceof split-lines at d values of a curved-crystalgraphite monochromatorand CuKcr 2.M2-2.035 and 1.824-1.817A in the published radiation.Indexing andunit-ceil refinementutilized the o'anarakite", pattern of and thesesplits are adequately program POWLS, a routine originally written by E.J. indexedonly with the monoclinic cell. In their study of Gabe and subsequentlymodified by J.T. Szymafski. Zn-ich paratacamiteoKracher & Pertlik (1983) As only small quantitiesof material were availablefor reported that they were unable to obtain the original some samples,all were mormted q/ith acetoneon a specimen of "anarakite', but they noted that the '2ero-background"plate scannedat4o 20 per minute, ooanarakite" unit cell of can be transformed to that and all peak maxima were checked manually. An of the monoclinic phase of Cur(OII)3Cl synthesized iterative procedurewas employedin the least-squares by Oswald & Guenter (I97L). The Oswald & refinements,with several cycles used in the progres- Guenter(1971) phase has a 11.83,b 6.822,c 6.1.66A, sion from low-angle intenselines to the higher-angle P 130.62", and application of the Kracher & Pertlik lines. Special atiention was paid to peak widths, and (1983) transformation-1 0 0/0 -1 0/1 0 2 gives a unit any lines showingbroadening attributable to overlapof ceUclose to that of anarakiteClable 2). lines were disregardedin the final refinements. In summary,our results indicated that the zincian paratacamitefrom Anarak is rhombohedral,and only Effect of CUCI2concentration the weaknessof the supercellreflections distinguishes it from previously reported rhombohedral panta- To define the preferredconcentration ofCuCl2 for camite. Thus, the monoclinic cell reportedby Adib & the synthesis,200 mL of NaOH solution werepumped Otteman(7972) for'oanamkite"remained unexplained, at 100 ml/h into 200 mI of CuCl" solution heatedto but type'onnarnkite"contains moreZn thanwas found 95"C. The CuCl2solution initially was at its naturalpH in the material examinedhere. Thus, we speculated value of approximately2, and the CuCl2concentration that the rcle of.Zn is possibly stucturally crucial, and was varied from 0.15 to 1,.0M; the molar ratio this aspectwas accordingly examinedin a series of OH-/Cu2+was fixed atunity in all the experiments.The synthesisexperiments. productsmade from solutionscontaining 0.5 or LA M CuCl2were difficult to filter and containedgrains of a Snrnrss Pnocnpunss dark phase;the productswere subsequentlyshown by AND ANALYTICAL Mgtnots X-ray-diffraction analysisto contain CUO in addition to the monoclinic phaseof Crg(OII)3Cl as synthesized All syntheseswere conductedusing reagent-grade by Oswald& Guenter(1971). By contrasLthe products chemicals and the direct precipitation procedure synthesizedfrom the more dilule CuCl, solutions outlinedby Sharkey& Lewin (LWD. A known volume consisted only of the monoclinic phase, containing of solution containing appropriateconcentrations of approximately6OVo Ct and l6VoCl [ideal Cu2(OII)3CI: Ctrclz, ZnCl2, or Zn(NOr)2 was placed in a glass 64.l9VoCu, L6.60VoCl, 23.89 wt%o OlIl. A slight reactor, which was heated to 95'C to minimize the excessofwater wasrecorded in all ofthe analyseseven possible formation of amorphousphases. A known thoughthe precipitateswere dried for 24hatl1"0"C. A volume of NaOH solution at room temperaturewas relatively constant2.61.7 g of precipitatewere formed pumped at a constantrate (<100 mlrh) into the hot for CuCl2concenftations ranglng from 0.15 tn 0.25 M. CLINOATACAMITE. A NBW POLYMORPH 65 Similarresults were obtained when 0.154.25 M CuCL solutionswere pumpedinto an equal concentrationoi NaOH solution heatedto 95'C. On the basis of these resuh$,most of the subsequentexperiments were done t oo a by pumping NaOH solution into a 0.2 M C1rCl2 a a solutionheated to 95oC. o/oCu Effect of hCl2 and Zn(NOj)2 concentratiow aa o Figure 1 illustrates the effect of. t}te Zn chloride N concentration on the compositions of the products 20 o/"Cl made by pumping 300 mL of 0.066 M NaOH at 100 ml/h into 100 ml of 0.2 M CuCl2 solution at a 95"C: i.e., 0.02 moles of NaOH were added to ; 0.02 moles of CuClr. In all instances,a relatively . foZn constant 1.2-1.5 g of precipitate were formed. Chemical analysisof the precipitatesshowed that the Zn contr;rrt increased systematically as the ZnCl, concentrationof the 0.2 M CuCl" solution wal increased from 0.0 to 5.5 M ZnCl".T]FreCu contentof o2468r0 the precipitatesdecreased as the Zn conlentincreased. (mol/L) X-ray-diffraction analysis of the products indicated lZnClzl only Cur(OH)rCl or (Cu,Zn)2(OlD3Cl. FIc. 2. Compositionsof fheproducts obtained by additionof Similar resultswere obtainedwhen using a stoichio- 0.1M NaOHto 0.2M CuC12solutions containing various metric deficiency of NaOH in a CuCl2 solution cotrcentrationsof 7ncl2. containing added.ZnCl2: Figure 2 illusltrates the compositions of the products made in experiments where100 mL of 0.1MNaOH werepumped at 6ml/h CuCl2,and the resultingproduct weights were typically into 200 mT. of 0.2 M OrCl" solutions containine 0.3 to 1.3 g. As the ZnCl2 concentrationof the CuCl2 various concenfrationsof ZnCir. In these tess, od! solution increasedfrom 0 ta 8.5 M ZnCLr, the Zn 0.01 moles of NaOH were added to 0.M moles of content of the precipitate increasedfrom 0 to about 97o Za. The frend is comparableto that shown in Figure l, and as the Zn content increases,the Cu content declines.The Cl content drops slightly with increasing ZnCl2 concentration,and this observation also is consistentwith the data illushated in Figure 1. All the products were shown by X-ray-diffraction analysisto consistonly of X2(Otl)3Cl-typecompounds (X= Cu or Cu,Zn). Figure 3 illustrates the corresponding results obtainedwhen 300 mL of 0.066 M NaOH solution ml N (0.02moles) were pumped at 100ml/h into 100 of M CuCl2solution (0.02 moles) containingvarious o 0.2 concentrationsof Zn(NOr)r. The results are approxi- a presence %cl mately the sameas those obtainedin the of 3 ZnCl2. Increasingthe Zn concenfrationsof the CuCl2 solutionresulted in an increasein the Zn contentofthe producg and a corresponding decreasein the Cu a-o/oZn content. The Cl content also declined slightly. The presence of. 4 M Zn(NOl)z resulted in a product containingapproximately 9VoZn, whereas a4 MZnCl2 gave precipitate containing about 5VoZn. o2468 solution a X-ray-diffraction analysis showedthe products made lZnCl,l(mol/L) from solutionscontaining O to 4 M 7n(NO3)2to consist only of X2(OH)3Cl-typecompounds; by contrast, Frc. l. Effect of ZnCl, concentrationson the conpositions of greater than 4 M resulted the productsmade by pumping300 mL of 0.066M NaOH, Zn(NOl)z concentrations at 100 ml/h, into 100 mL of 0.2 M CluCl, solution ar in the precipitation of zincian gerhardtite, 95'C. (CuZnXNqXoH). 66 TIIE CANADIAN MINERALOGIST ratio on the amountand compositionof the products, 200 mL of solution containing0.2, 0.75, 0.10, or 0.07 M NaOH were pumped at 6 ml,h into 200 mL of 0.2 M CuCl2- 4 M'ZnCl2 solutionat 95oC.The NaOII/CuC12molar ratio seemsto havehad little effect on the compositionof .the precipitates,which consis- tently contained abottt52ZoCn,57o Za, and LSVoCl. (.) The principal effect 0f decreasingthe relative amount N of NaOH was that the amounl of precipitatedecreased linearly with the concentrationof NaOH. s X-Rev Srupv oF SYNTHEITICPnolucrs 3 The productsofthe synthesesare fine-grained green to greenishblue powders,the latter reliably indicating a substantialuptake of Zn. Nl of the products were examined visually by Guinier - de WoLff X-ray pattems obtained with Co X-radiation. The pattems lZn(No")rl(mol/L) were classifiedinto two groups,.onebeing that of the Ftc. 3. Compositionsof theproducts obtained by additionof simFler pattern characteristic of our spgcimensof 0,066M NaOH to 0,2 M CtCl2 solutionscontaining the Anarak mineral, and the otlier referring to the variousconcentrations of Zn(NO3)2. slightly more complex pattern typical of the mono- clinic Cu2(OI!3Cl phase synthesizedby Oswald & Guenter (1971; PDF 25-l4n). Preliminary unit-cell dimensiols, based on a hexagonalcell with a 6.84, Attempts to preparethe end-memberZn analogue c L4.06 A, were subsequentlydetermined by least- of Cu2(OH)3Clby pumping NaOH into various squares refinements of partial diffractometry data. ZnCl2-Zn(NO3)2solutions at 95'C were unsuccessfrrl. Plots of a and c versw 7,n in aloms per formula unit The pumpingof small aaounts of NaOH did not cause showedthat the transitionfrom the Oswald& Guenter ny Zn precipitation, whereasthe addition of large (1971) monoclinic phaseto the Cu-Zn rhombohedral amounts of NaOH resulted in the precipitation of phase occurs apporimately between CugaZn6and simonkolleite,ZI5(OIDsC12.H2O. Cag{as Gig. ).The tansition zone in somepattems was found to be clearly recognizableby a merging of Effect of (OH\/OP+ malnr ratio diffraction lines, but there was some overlap in the classification of individual sampleswithin the zone To investigale the effect of the (OIDlCu2+ molar (Fre.4). "( e.e3 oo o d ^^t 6.44 to 4r FIc. 4. Plot of a and c dimen- aoo^o sions yerszs formula per- o l cenf2ge 7n in synthetic a ^l (Cu,Zn)2(OlI)3Cl(Table 3). Open circles: mono- A clinic phase; solid trian- gles:hexagonal phase. All 101520 samples indexed on a hexagonalcell. o/oZn in formula (Cu,Znl CI-INOATACAMITE, A NEW POLYMORPH 67 TABLE3. SYI.{THB'fiC(qr,Ar)b(Ott}Cl SERIES INDDGD WITH in most samples,several diffraction lines in the patterns HD(AGOMLCELL are extraneousto the rhombohedralcell of parata- Saryle Fsrula camite as grven by Frondel (1950). Theseexftaneous o/oZn nrmber a (A) c (A) ThF lines were satisfactorilyindexable with the 6eaqelinie cell of Oswald& Guenter(1971). l-6 0 6.824(13) r4.0r7Qr) M AD2 r.9 6.Wt) 14.1070e) M Thus, the initial premise that the synthesisseries 44 L6 6.83{0 14.03(8) M would indicate a tansition from a Cu end-member 7 3.r 6.832(3) r4.04(8) M represented by paratacamite (rhombohedral) to a 45 4.0 6.83411) 14.0441) M AD3 42 6,838(8) 14.0550o M potentially monoclinicZn-rich memberwas exactlythe AD4 4.8 6.840(? 14.0630t M reverseof what was found, i.e,othe syntheticCu end- Plo+ 62 6.840(D r4.04{3) H member is monoclinic, and the Zn-ich membersare PARA46 6.6 6.834(t v.uq7) M Pl9 6,7 6.Sq4) 14.03{t M rhombohedral. The maximum Zn content of the P8 7.4 6.835(8) 14.04q14) M synthetic series is 14.8 wt.%o,corresponding to P51A 7.6 6.S9(t) 14.w,{2) H n0 (Cur.sF"o.sd(OHLCl, which is higher than the Za 7.8 6.S9(l) 14.051(3) tYt of ooanarakite"as described by Adib & P9 8.6 6.85(3) r4.04{0 M content w E.6 6.e8(1) r4os6(1) H Ottemann (1972). The poorer quality, as marked by PA e.0 6.E39(l) r4.0qr) H increaseddiffirseness of the X-ray patterns,of the two P48 92 6.8ap) 14.061(4) H mostZn-rich samplesin the series(Fig. 4) suggeststlat P51B 9,4 6.840(t) t4.vt3(2) H P10 10.5 6.8410) 14.05(2) H the upper limit of Zn substitution in our synthetic P5lC u,6 6.84q1) v.alz) H paratacamite(rhombohedral) may have been closely P50 rz0 6,w2) M.s7q2) H HoweveroKracher & Pertlik (1983) P51D approached. r18 6.E4ql) 14.w3Q) H parata- P49 13.5 6.838(3) r4.071(0 H obtained an electron-microprobeanalysis of P47 14.0 6.w7) 14.093(9) H camite from the Herminia mine, Chile, in which the Dl< t42 6.5a/J) l4.u79Q) p3E Zn contentis L6.2 wt.Vo;this zincian paratacamitewas r43 6.84?14) v,wa n group Pt2 15.0 6.8430) 14.056(3) H confirmed by them to be rhombohedral,space P39 16.3 6.84q1) R3, with cell dimensionsas reportedby Fleet (1975). p Trr Nsw M[.{BAL Cr.noeraceuns The preliminary X-ray resultsshowed that there are problemsin indexing all of the diffraction lines on the This study of paratacamitewas initiated because basis of a hexagonal cell. Subsequentcollection of diflerences were observedin the X-ray patterns of precisediffractometry data confirrnedthat, althougha natural specimensof paratacamite.When it became small amountof contaminationby atacamiteis present apparentfrom the synthesisexperiments that neither TABLB 4. UNIT CELIS OF CLINoATACAMIIE AND RELAIED Clr, (cu,zn), AND co PHASES crL(ol}rcx ot(oI{LcI (cu,zlxottcl (Gtzrxolrlo clt(oH).o aloIl)bcl cq{oDra oor(oHlo 'a@klb' boElkdib Mne lqiee sylthfdc dho@db .th@mte (PDF8-88) (PDFX-94t) (PDP25-325) ((b[er (PDF2tl427). (8yir!.do)' (rbtsddyt (syBbedc)6 a,A s.zLs 6.E92 11.901 t3.654 11.83 6.17 6.157 6.E4 b,L 6.t% 9.080 6.830 - 6.922 6.92 6.814 c,A s,632 6.055 10.162 t4,u\ 6.t6 9.t2 9.105 14.50 ff c2.7s - tLz.n - 130.62 9.63 99.65 sysEm* ltr OM RM MMi rp@ 9{|o$p nln Pne cc,C2/c fl nJd F2tln P2tln frn rrr - @ltdq O - oithoftooblg,R E lhdlboh.dnl l. Adlb & O@ (1972), Kall Xrn El!g, A@ak, t@ 2. Ft€ (1C7t, Stsft tus, Chilq @ €ll fi@ shgte a cotype specimenof "paratacarnite"from Remolinos, specimens,such as those from Sierra Gorda and the Chile (USNM 95L46), which also was used in the holotype from Chuquicamata, all three minerals descriptionof paratacamiteby Frondel(1950). Energy- coexist. dispersionanalyses of thirteen grains confirmed them The relative stabilitiesof atacamiteand paratacamite to be Zn-free,as reported in Frondel(1950), but X-ray- have been widely discussed,most recently by Woods diffraction patlerns of four grains showed all to be & Garrels(1986), Pollard et al. (1989),Buruzova et al. clinoatacamiterather fhan paratacamite.Nevertleless, (1989),and Hannington(1993). Pollard et al. (1989) various discrepanciesin the optical propertiesremain concludedthat paratacamiteis the thermodynamically unexplainsd;most notableis that rve find paratacamite stable phase at ambient temperatures.It is possible, to be uniaxial negative,whereas the sign is reportedas however, that the phasesynthesizedby Pollard et al. uniaxial positive in Palacheet al. (L95L). was clinoatacamiterather than paratacamite,exactly as was the case in the experimentsby Walter-Irvy & Composition Goreaud(1969), Oswald & Guenter (L97I), Sharkey & Lewin (I97I), and in this study. There is general Electron-microprobeanalyses of grains from the agreementthat botallackite,which is of limited natural Chuquicamata specimen M32176) were obtained occurence, is metastablewith respect to the other using a JEOL 733 instrumentoperated at 13 kV, with a Cu2(OH)3Clpolymorphs. Of ttrese, atacamite is ZAF correctionprogram and CuS (Cu) and NaCl (Cl) probably the most widespreadin geological occur- as standards.Zinc and Ni were not detected.The rence. mean analytical results (and ranges) are:.CuO 74.7 (73.4-76.0),Cl 16.5 (L5.7-17.2),(HzO)"a" 13.5, sum SussrrnffIoNs oF Co ANDNi ron Cu 1M.7, lessO = Cl 3.7,total 101.0wt.Vo.T\e empirical formulafor O + Cl = 4 is Cu1.e6O3.6H3.1rClo.r,ideally In the experimentalstudies concerningZn substi- Cu2(OII)3CI.The latterrequires O.rO 74.49, Cl 16.60, tution, it was showntlat partial solid-solutionoccurs in H2O 12.66, sum 103.75,less O = Cl 3.75, total clinoatacamite,and more extensivelyin paratacamite. L00 tut.Vo. The supercellreflections in zincian paratacamiteare extremely weak, and unless special precautions Distribution are taken to detect the full -cell, the apparent cell correspondsto a 6.8, c L4.0 4,, possible space-group Clinoatacamite from Chuquicamata, Chile R3rz. Rhombohedral compounds with these cell (M32176), occurs with atacamite, paratacamite, dimensionsand space grotp R1m are known as the gypsum, and alunite on a quanzose matrix. synthetic phases Fe2(OH)3C1,Mn2(OH)3C1, and Clinoatacamitealso was found in a specimenfrom Co2(OH)3C1.In his description of the structure of Calumet Michigan (ROM, M26081), from Mason Co2(OH)3C1,de Wolff (1953) suggested that Pass, Lyon County, Nevada (Cureton 4731), ftom Cu2(OH)3Clmight also be included in this structural Chuquicamata"Chile @inch 508), from Sierra Gorda fype. This possibility was accordingly eaaminedia a mine, Chile @M 86958),fromWallaces Gully, Mount seriesof synthesisexperiments. Painter, South Ausralia (South Australian Museum G13208), from Wallaroo mines, Kadina, South Co-4 u synthesisexp eriments Australia (South Australian Museum G11409), and from Remolinos,Chile (USNM 951"46).Three speci- Co2(OII)3CIwas synthesizedby pumping 200 mL mensfrom the type locality for "anarakite" (Kali Kafi of 0.2 M NaOH solution at 25 mI-Jhinto 200 mI . of mine, Anarak Province,Iran), but obtainedfrom tbree O.2M CoCl2mediumheld at 95oC.The X-ray pattem different sources (ROM M35,149; National Mineral of the precipitateis distinct from that of paratacamite, Collection NMC 14654; Pinch collection "zincro- and is in good agreementwith the powder data given sasite") proved to be paratacamite. Additional by de Wolff (1953)for Co2(OII)3CI. specimensthat proved to be paratacamiteare from The effect of the concentation of CoCl2 on the Churchill Buttes, Lyon Counfy, Nevada (M23078), synthesisof Cu2(OII)3CIwas investigatedby adjusting from Levant mine, Comwall, England@132265), from the 0.2 M Cuclz medium to 0.2 M (CoCl2 + Cuclr. Nangeroo mine, Murrin Murrin, Westem Australia That is. the Cu concentation of the solution decreased 0433193), from the Carr Boyd nickel mine, Westem as the Co concentration increased. Increasing the Ausfialia (unnumberd Curetou), and from the Otter CoCl2concentration from 0.0 to 0.05Mhad little effect Shoot,Kambalda WestemAustralia (SouthAustralian on the composition of the products; the Cu content Museum G12245). The Carr Boyd and Otter Shoot was approximately 57Vo, and the Co content was specimensgave slightly different X-ray patterns,and consislently less than L wt.Vo.Increasing the CoCl2 proved to be nickeliferous. concentrationto greaterthan 0.05 M, with concomitant The above study shows that atacamitecommonly reductionsin the CuCl2concentrations, caused a linear coexistswith paratacamiteand clinoatacamite.In some increase in the Co content of the products and a 70 TIIE CANADIAN MINERALOGIST /** J n / O / C) z 5 o a s x 920 5ro o 7\ 0.20 lCoClzl(mol/L) lNiClrl (mol/L) Ftc. 5. Compositionsof the productsobtained by addition of Ftc. 6. Compositions of products obtained by addition of 0.2 M NaOH to 0.2 M (orICI"+ CoCl). 0.2 M NaOH to 0.2 M (CtCl2 + NiCl). simultaneouslinear decreasein the Cu content(Frg. 5). also decreased systematically. X-ray-diffraction In all the syntheses,the Cl contentremained relatively analysis of the products made from solutions constantat aboutl5%o CL containingmore than 0.05 MNiCl2 showedincreasing Guinier - de WolffX-ray diffraction pattemsof the amountsof Ni(OH)2. The X-ray results, coupledwith precipitatesshowed that cobaltoanclinoatacamite was the reducedCl contents.indicated that the increasein formed to a maximum of 5 wt.Vo Co, i.e., the Ni content of the precipitates was due to the (Cu,..rCoe.17)(OtI)3C1.Bulk samplescontaining higher admixtureof Ni(OII)2 and Cu2(OII)3C1. Co values were found !o be two-phasemixtures of Efforts to suppressthe formation of N(OII)2 by clinoatacamiteand rhombohedralCor(OH)rCl. As for varying the amount of NaOH pumped (0.1.or 0.2 M the Cu-Zn series, however, tle transformatiou NaOlf), by decreasingthe pH of the NiClr{uClt boundaryis not sharp:two-phase products were found solution from 5.5 to 2.5, or by increasing the total in samFlescontaining as little as 3.2 wt.VoCo. Thus, chloride content of the NiCl2{uCl2 solution by the the rhombohedralCo phaseis distinct, and relatively addition of 0.2 to 2.0 M LiCL were unsuccessful. little Co substitutionwas effectedwith the conditions Nickel hydroxidewas detecledin major amountsin all of synthesisthat were utilized. products. Although a Co analogue of Cu2(OIfrCl existsowe werg not able to synthesizethe correspotrd- Ni-Cu synthesisexpertmcnts ing Ni analogue. Efforts to prepare Ni2(OH)3Cl or Ni-bearing Nickelifurous paratacatnite Cu2(OII)3CIwere not overly successfulnas is indicated by the data in Figure 6. The experimentalconditions Although we were unableto effect an uptakeof Ni qrsls similar to thoseconducted for Co. Increasingthe by Cu2(OI!rCl, the paratacamitefrom the Can Boyd NiCl2 concentationfrom 0.0 to 0.05 M had little effect nickel mine, Westem Australia, showsX-ray diffrac- on the compositionof the product; the Cu, Cl, and Ni tion-line shifts that are caused by the presenceof contentsme approximately6LVo, l5%o, and less than appreciableamounts of Ni in solid solution. Electron- 0.5 wt.Vo, respectively. X-ray-diffraction patterns microprobeanalysis showed some variation in Ni{u showedthese products to contain single-phaseclino- ratios, and sevenquantitative analyses gave an average atacamite.Increasing the concentrationof NiCl2 (andrange) of Cu 49.9 (48.L-52.7),Ni 8.5 (6.4-10.3), beyond 0.05 M resultedin a rapid increasein the Ni cl 16.0 (14.r-16.7), (oH)"a" 25.6 Q5.V26.8). The contenl of the productsand a correspondingdecline in compositionwith the highest Ni content (I0.3 wI.Vo) the Cu content;significantly, howeverothe Cl content correspondsto (Cu1.62Nis38)(OID3.1sClt.ee,and the CLINOATACAMITE. A NEW POLYMORPH 71 TABT,E5. X.RAY POWDERDATA FORNICKELIFEROTJS the validity of o'anarakiteo'.The observation in the PARATACC,MNE,CARR BOYD [4IIIE, IVESTERNAUSIRELIA synthesis experiments that high Zn contents in {" d* d* hH ,(" d* 4"b hH (Cu,Zn)2(OII)3Cllead to the formation of paratacamite (rhombohedral)rather than 4 meaqslinis structureis at 100 5.4 5.449 101 <5 1.743 1.74 125 25 4.62 4,637 m3 q 1.710 1.710 220 variance with the monoclinic symme0y reported for 10 4.51 4.5W 0r2 <5 l.ffi 1.660 m "anarakite". The specimensexamined here from the 15 3.415 3tn 110 <5 1.650 1.650 V27 s 3.m4 2,W 104 5 1.630 1.631 131 type locality for "anarakite" indicate that there is 45 ZEg 2.W 021 5 L6A2 Ltu n3 substantialvariation in the ratio of.Cn:Za, andpossibly 80 2,751 2.752 113 l0 1.5@ 1.s00 208 the fragmentexaminedby Adib & Ottemann(I972)by 25 2.n5 Z'n' 202 15 1.485 1.486 2t7 15 2316 2319 m6 5 1.472 t.472 401 single-crysta1X-ray methodsdiffered in composition 70 2253 2255 0A l0 Lw 1.448 u2 from their chemically analyzedsample. The recogni- <5 22t2 2210 2tt 5 LW L.&9 119 15 2.02.r' L@8 255 2rJ 1376 1376 26 tion by Kracher & Pertlik (1983) that the unit cell of <5 1.918 1.919 116 10 1.363 1362 N4 "anarakitp" can be transformedto that of the mono- 15 1.884 1.884 107 5 1.3s3 r.352 321 phase Guenter(1971) is 30 1.816 1.817 033 <5 lJ08 13Ut 045 clinic synthetic of Oswald & significant in that this synthetic phasecorresponds to I 14.54.m Gandolfifitq CoKaradidico bdocd wi*r hoogmal ubcell the mineral now called clinoatacamite.Thus, it is a 6,t39(2\ 13.911(4) c A" possibleto speculatethat the single-crystalfragment of 'oanarakite"may havebeen clinoatacamile. The X-ray powder patternsof atacamiteand botal- lackite are distinct from each other and from those averagecomposition is (Cu1.6eNiq31)(OH)3.2aClo.ez.of paratacamiteand clinoatacamite.The pattem of The cell dimensionsfrom the indexedpowder pattem clinoatacaiaiteis slightly more complex than that of (Table 5) are similar to tlose of z,incianparatacamite. paratacamite,and one of the distinguishingfeatures is Optical examinationof the Carr Boyd nickeliferous the clusteringof fo_grdiffraction lines at 2.713,2.339, paratacamiteshowed it to be uniaxiat negative.Nickel 2.266, and 2,243 L for clinoatacamite,whereas only et al. (1994) reported the occurrence of nickeloan firye linss appear in this range for paratacamjte paratacamitewith up to L7.4 wt.7o Ni at the (Table 1). Published X-ray patterns for synthetic Widgiemoolthadeposit, Western Australia, and it too "paratacamite", including the PDF standard for is uniaxial negative @.H. Nickel, written corlm., paratacamite (25-142:7), pertain to clinoatacamite 1994). rather than paratacamite. CoNctusroNs ACKNowl-mGHuH{Ts Clinoatacamiteis the third well-definedpolymorph The assistanceof CANMET personnelD.R. Owens of Cu2(OH)3C1,and will be the fourth if it is and T.T. Chen (microbeam laboratory), P. Carridre demonsfta0edthat paratacamite exists at the end- (X-ray), and O. Dinardo (syntheses)is much appre- membercomposition. Althoughthe original analysisof cialed.Specimens of paratacamiteand related minerals paratacamitefrom the Generosamins, Qhile @l\4 examinedin this study were kindly provided by J.A. 86958)did not reportthe presence ofZn (Smitl 1906), Mandarino and R.I. Gait @oyal Ontario Museum), subsequentelecton-microprobe analysis by Embrey & A.J. Criddle (The Natural History Museum), H.G. Jones (in Kracher & Pertlik 1983) showed that this Ansell (National Mineral Collection, Geological specimen contains 2.45 wt.Vo 7n, which we have Survey of Canada),W.W. Pinch @ochester,N.Y.), confirmed for our portion of the specimen.Thus the A. Pring (South Australian Museum), and P.J. Dunn fragment used by Fleet (1975), also from the same (Smithsonian Institution). Editorial comments by specimen,for the X-ray structurestudy of paratacamite R.F. Martin and critical reviews by C.N. Alpen and is likely Zn-bewing, as had been deducedby Kracher P.C. Bums were of significant benefig and we are & Pertlik (1983), Effenberger (1989), and Burns particularly grateful to Dr. Burns for bringing to our (L994). Kracher & Pertlik (1983) suggestedthat the attentionthe publicationby Kracher& Pertlik (1983). sffuctureof paratacamiteis stabilized,relative to those ofatacamiteand botallackite, by the partial substitution Rmmcrs of Zn for Cu in paratacamite.The resultsobtained here supportthe conceptthat the formation of paratacamite ADrB,D. & Orrrveml, L (1972): Ein neuesmineral, (Cu,Zn)2(OH)3C1, mine, is favored by the presenceof substituting cations aus der Kali-Kali Provinz Anarah zentralhan. Neueslahrb. Mineral,,Motwtsh, such 7n as or Ni, eventhough these may be as little as 335-338. 2-4 wt.Vo,In the absenceof thesecations, the mineral more likely to form is clinoatacamite rather than Btmrs, P.C. (L994);The Stereochcmistryof C*+ Orysalt paratacamitg, Mfuerals:an Ab Initio MolecularOrbbal Approach. The results of this study add to the doubts about Ph.D.thesis, Univ. Manitoba Winnipeg, Manitoba. tz THE CANADIAN MINERALOGIST BurtzovA, G.Yu., Srrmsrsm.c, L.YE., VonoNnr,B.I. & PALAcTD,C., BmuaN, H. & Fnol.oaL C. (1951): TheSystern Gon'rove, N.V. (1989): Atacamite in metalliferoussedi- of Mineralogy 2. Jobn Wiley & Sons,New York, N.Y. mentsof the Atlantic.Dokl. Eanh Sci.3(D.158-161. PoLARD,A.M., Tuouas, R.G. & Wn:,teus, P.A. (1989): EFFE\tsm.cE&H. (1989): An uncommon Cut2{lou coor- Synthesisand stabilitie,sof the basic copper(tr) ctilorides dination polyhedron in the crystal structure of atacamite,paraacamite and botallackite. Mineral, Mag. KCu3(OH)r[(AsO)H(AsOf] (with a comparison to s3,5s7-563. relatedstructure types). Z Krtstallogr. l8E, 43-56. PRnrc, A., Sr.row, M.R. & TIEK$rK, E.R.T. (1987): FLE-I, M.E. (1975): The crystal structue of paratacamite, Paratacamitefrom Soutl Australia.Trans. Roy.Soc. South Cu2(OH\Cl. Acta Crysullo gr. B3l, 183- 1 87. Aust.3,123-1,28. FLe$cHR, M. (193): New mineral names,Am MineraL SS, SHARIGI,J.B. & LswN, S.Z. (1971): Conditions goveming 560-562. the formation of atacamiteand paratacamite . Am Mfueral, 56,t79-t92. FRoNDEL,C. (1950):On paratacamiteand somerelated copper chlorides.Mineral. Mag. 29, 3445. Surq G.F.H. (1906): Paratacamite,a new oxychloride of copper.Mineral, Mag.14, 170-177. HaNN${crol.I, M.D. (1993): The formation of atacamite during weathering of sulfides on tle modern seafloor. War,rsn-Luw, L. & GoREAUD,M. (1969): Sur la formation Can. M ineral. 31. 945-956. des chloruresbasiques cuivriques en solution aqueusede 25 t2A0"C. Bull. Soc.Chim. France1969(8),2623-2634. Hawrnomm, F.C. (1985): Refinementof the crystal structure of botallackite.Mineral. Mag 49, 87-89. Wnr,rs,A.F. (1949):The crystal structue of atacamiteand the crystal chemistryof cupric compounds.Actd Crystallogr. KRAcrrm.,A. & Pnnn-rc, F. (1983): Znkreicher Paratacamil 2. 175-180. Cu3Zn(OID6C12,aus der Herminia Ming Siena Gord4 &ile. Ann.Nanrhist. Mus. Wien85l*,93-97. DE WoLFF,P.M. (1953): Crystal strucfre of Co2(OII)3C1. Acta Crystallogr. 6, 359-360. NrcKa, E.H., Gorn, J.F,M. & Ganrnq:,, B.J. (1994): Secondarynickel mineralsfrom Widgiemoolth4 lVestern Woons, T.L. & Gannss, R.M. (1986):Phase relations of A:astraha.Mbural. Rec. 25, 283-291.,302. some cupric hydroxy minerals. Econ, Geol. 81, 1989-20W. & MaNpanwo, J.A. (1987): Proceduresinvolving the IMA Commission on New Minerals and Mineral Names, and guidelines on mineral nomenclature.Caa Mineral.?5.353-377. OswArD,H.R. & Gunum" J.R. (1971): Crystal tlata on paratacamite T-Cu2(OII)3C1.J. Appl. Crysnllogr. 4, Received September 19, 1994, revised. manuscript accepted 530-531. August7,1995.