Canadian Mineralogist Vol. 18, pp. 191-195(1980)

SOLIDSOLUTION IN THE ADELITEGROUP OF ARSENATES

J.L. JAMBOR, D.R. OWENS AND J.E. DUTRIZAC Mineral SciencesLaboratories, CANMET, Depaftment of Energy, Mines and Resources, 555 Booth Steet, Attuwa, Ontario KIA OGI

AssrRecr TABLEI. IiIINERALSOF THE ADELIIE GROUP Nare composltlon a(l) b(l) c(A) Reference rr.a2. ('19511 adellte CaMqAsO,OH- 7.47 8.94 5.88 Palache and specimens from , 7.525 8.895* 5.850 PDF24-208 Namibia (South West Africa) are commonly zoned Palacheal q2. (1951) austlnite CaZnAsO,0H' 7.43 9.00 5.90 in color and composition. Microprobe analyses and 7.506 9.046 5.932Radcliffe a Simns X-ray powder-diffraction studies indicate extensive conrchalcrte cacuAso,oH 1.42 s.2o t.* []?llh ordz. (1s511 e 7.3e3s.220 5.830 &srmns Clu-Zn and Pb{a substitutions, which rep- iisill". (CaCu 9.14 5.91 Palachert 02' (1951) resent solid solution among conichalcite duftlte PbCuAs0,oH* 7.52 (CaZnAsOaOH) 7.51 9.14 5.9 PDF6-0322 ASO"OH), and duftite 7,81 9.19 6.08 PDFl4-169 (PbCuAsO.OH), group all of the of arse- gabrlelsonite PbFeAso40H7.86 8.52r 5.98 PDF20-583 nates. Cell dimensions of end-member duftite are PbZnAso4oH Taggart & Foord a 7.778(4), b 9.207(3), c 6.000(5) 4., v qzg.l Ar. Keywords: adelite group, duftite, austinite, coni- chalcite, Tsumeb, compositional and color zoning tion and to ascertainits possibleuse as a powder- solid solution, X-ray powder data, in minerals, A microprobe analysis cell volumes. diffraction standard. showed that the material varied substantially in that Cu was fairly constant Sovtvternp Pb, Ca and Zl, but under the expanded beam used for the anal- ks 6chantillons de duftite et de conichalcite de ysis. The material seemed to belong to the Tsumeb, Namibie (Afrique du Sud-Ouest) montrent adelite group, but a precise identification could souvent une zonation en couleur et en composition. not be made. Re-examinationof the above speci- Les 6tudes ir la microsonde et d la diffraction X men. as well as others labeled "duftite", was sur poufues indiquent des substitutions importantes undertaken and the results form the basis of CvZn et Pb{a. et donc des solutions solides this report. Part of the Tsumeb specimen has entre la conichalcite CaC\AsOaOH. I'austinite been depositedin the National Mineral Collec- CaZnAsOOH et la duftite PbCUAsOOH, toutes trois tion, Ottawa (NMC 61459). membres du groupe de I'adelite. Les dimensions de la maille au p6le duftite sont a 7.778(4\, b 9.207(3), c 6.000(5)4,, v qzs.t L". OntcrNlr Tsutvtss SpecrvEN (Iraduit par la R6daction) The specimen is dark green and about 3 Mots-cl4s:,groupe de fadelite, duftite, austinite, cm in diameter. Broken and cut edges show a conichalcite,Tsumeb, zonation en composition random oscillation of color zones, all in muted et en couleur dans les min6raux,solution solide, shadesof green, that conform with the coarsely diffraction X sur poudres,volume de la maille. botryoidal surface. Microscope and microprobe examinations of a polished thin section revealed INtnoouctloN that color and composition zoning occurs on such a fine scale that areas sufficiently large Six members of the adelite group of arse- and homogeneous for microprobe and X-ray nates are known (Table 1). Although published powder-diffraction analysesare difficult to find. chemical data indicate that little solid solution occurs among members of the group, all are Microprobe analyses believed to be isostructural, with P2t2r2t (Radcliffe & Simmons 1971). Analyses were pedormed with a Materials A specimen labeled "duftite" from the type Analysis Company model 40O electron micro- locality, Tsumeb, Namibia (South West Africa), probe operated at 2O kV and a specimen cur- was examined in 1976 to obtain X-rav verifica- ient of O.O: pn. Counting periods of l0 seconds L91.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/191/3445757/191.pdf by guest on 01 October 2021 r92 THE CANADIAN MINERALOGIST

- TABLE2. IIICRoPRoBEANALYSES 0F TSUMEB (Nl'lc 61459) PLUMBIAN'ZINCIAN CoNICHALCITE

green l. Color'less 2. filediun green 3. Dark green 4. Bromish av. tri?- moT. ranjJT'f rfl-Tt'-@--ranqe-;'fr7 tf,-frT-@@ av.-ffi-@'@ Ca0 15.4 .274 12.0-17.6 14.3 .254 13.0-17.8 9.5 .170 9.'l-10.5 14.7 .262 12.9-15.7 Pb0 15.4 .069 8.9-22.0 15.5 .070 9.2-18.7 29.5 ,132 28.1-31.4 17.6 .079 14,4-22,4 Cu0 19.5 .246 16.8-21.9 20.2 .255 19.3-22.0 21.7 .272 21.0-22.4 21.5 .271 20,7-2?.5 Zn0 9.1 ."112 7.8-11.8 7.7 .095 6.1-8.8 3.2 .040 2.9-3.7 6.1 .075 4.9-7.5 <0.1 0.t - 0.1-0.1 <0.I <0.1 l4n0 ??n 36.7-38.8 Asr0U 37.4 ,326 36.0-39.0 37.7 .328 36.8-39.6 .287 32.1-34,4 37.9 .330 96.9 ,r.t 97.9 = av. Ca:Pb= 78:22 av. ca:Pb.56344 av. Ca:Pb 80:20 = Cu:Zn= 69:31 Cu.Zn.73:27 Cu:Zn 87:13

SQAtndahaa Dark green Almst colorless Alnost colorless av. r{t7-npT. rande, wtU av. wt% mol. range,Ht% a*-tt%-@-@ Ca0 I0.5 .187 10.2-10.9 10,2 .182 9.9-10.6 16.9 .301 16.6-17.2 Pb0 29.0 .130 27.1-29.7 27.4 .123 26.9-27.7 12.6 .056 l l.5-13.8 Cu0 23.4 .294 23.0-23.7 22.7 .285 22.3-?3.C 20.5 .258 19.3-21.5 Zn0 2.5 .03',1 2.1-2.7 3.0 .037 2.5-3.6 8.6 .106 6.8-12.8 I'ln0 <0.1 <0.1 <0.1 4s205 34.I ,296 33.4-34.8 ??a .295 33.1-35.3 39.7 ,346 39.1-40.7 ; 98.4 = av. Ca:Pb= 84:I6 av. Ca:Pb 59:41 = CurZn= 90:10 Cu:Zn 71:29

of end- and the following X-ray lines and standards genei.tyrepresented -conichalcite,.physical combinations were used: Pb Ma, galena; Ca Ko,, apatite; Cu membir duftite and austinite Ka, CuS; Zn Ko,, ZnO; Mn Ka, rhodochrosite; (rather than extensivesolid solution), then these powder As Lc, CoAs:. Areas in the polished thin sec- mixtures should have been detectableby tion of the Tsumeb specimen were selected as X-ray diffraction because the Ca-Pb-{u-Zn is large. The cell dimensions of the represent?tive-The of the various color ranges. variaiion microprobe analyses(Table 2) show that relevant members of the adelite group, although the different color zones are variable in com- similar, differ sufficiently that anomalously position and apparently represent extensive solid large diffraction-line broadening, as well as phases, solution in the adelite group. All the analyzed distinct lines for the individual should are zones have Ca ) Pb and Cu; Zn; thus the appear on 114.6 mm films. These features Tsumeb mineral is plumbian, zincian conichalcite. Al- not evident on X-ray patterns of the though one could infer from the first four material (Cu and Co radiations), but distinct analyses in Table 2 that conichalcite becomes diffraction-line shifts are present. These shifts darker green as the content increase$, are sufficiently large to indicate that the coni- analyses in another area of the section, con- chalcite end-member is absent in the Tsumeb sisting of numerous but narrow zones of dif- material. of ferent shades of green, do not confirm the Powder-diffraction patterns from several though apparent trend (Table 2). Analyses obtained the analyzed areas were sharp even from a second polished section give com- incorporation of multiple zones, as indicated by positions in the same ranges as those in Table 2 the composition ranges in Table 2, was una' and sonfirm the lack of correlation between voidable. To obtain comparisons with the cell color and composition. The presence of over dimensions given for austinite and conichalcite AOVo CuO in. the almost colorless areas is bv Radcliffe & Simmons (1971), MgO was added provide notable. subsequently to the X-ray spindles to back-reflectionsfor shrinkage corrections. Least- refinements were done with Cu Kcur X-ray-diffraction stud.y squares radiation 0, l.5405l A). Although the refined Few of the areas analyzed by microprobe parameters are near those of duftite and coni- were homogeneous,but the composition ranges ihalcite the PDF cell data for duftite differ were consistently those expected for adelite- so substantially (Table 1) that specific diqen- group minerals. If the compositional hetero- sions for the end member could not be selecte{.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/191/3445757/191.pdf by guest on 01 October 2021 THE ADELITE GROUP OF ARSENATES t93

'DUFTITE", TAELE3, X-MY Po$DERDAIA FoR DUFTITE, TSU}|EB,S.!.A. (pDF 14-169) TABTE4. IiIICROPROBEAMLYSES OF ROI'{I'I 29503

perlpheral clusteN I dmas dc" hhx I d"ul. hhL l c av. range' aY. {tg ran9e, -{n"us'r 40 5.03 5.00 o'il * !0 .96 1.97 240 Pbo 38.t .171 34.5-39.0 19.0 .085 ll.5-?3.4 30 4.60 4.59 020* ,^,^.fr.94,u ,.r, 013 CaO 6.2 .ll0 5.5-7.6 13.5 .241 11,9-1s.9 50 4.21 4.19 11lr I l.g3 400 CuO 23.2 .292 22.8-24.2 ao.t .JJo aa.9-ad.a 30 3.95 3.94 I 20r 50 1.87 1.87 331* Zno 0.6 .0@ 0.5-0.7 0.9 .012 0.9-l.I tn taa 2qa 2101 l0 1.85 1.84 401 tu205 30,2 .263 29.3-31.0 37,5 .327 35.9-39,4 100 3.26 3.24 201 10 1.82 1.82 . = 40 2,99 2,98 av. Ca:Pb 39:61 av. Ca:Pb 74:26 '1301oo2 l0'1.81 1.82 o42 . 97t3 80 2,85 2.84 10 t.78 t.78 420 CuZn.97t3 Cu27tr 80 2.65 2,65 221* lo 1.77 1.77 142 @ 2.57 2.57 13tr 051 '1010 2.48 2.48 3l or 30 I .71 1.71 l5lr 2.38 2.38 122 50 1.64 1.64 242 rowed from the Royal Ontario Museum. Both 50 2.28 2.28 212t 30 1.58 1.59 412 10 2.23 2.22 231 40 1.53 1.53 060 are from Tsu.meband both proved to be strongly l0 2.19 2.20 140 30 t.49 1.49 004 30 2.09 2.10 222 30 I.45 1.45 z5z zond. Microprobe analysisof one specimen (M im 2.05 2.06 132 30 1.38 1.38 403 29503) gave comllositions that vary from cal- ' lndices usedfor least-squaresreflnmnt. orlglnal cell: 4 cian duftite to plumbian conichalcite (Table 4). 7.81, 6 9.19, e 6.084;reflned cell a 7,716,b 9.178,c 5.9544 The other specimen (M 3485L) also proved for CuKolradlat{on. highly variable in composition and is plumbian conichalcite with an outermost zone containing Therefore, the PDF data were treated to least- appreciablevanadium in substitution for . squaresrefinement, and additional "duftite" spe- Four specimens labeled "duftite" were ob- cimens were studied. tained from the Systematic Reference Series of the National Mineral Collection, Ottawa. After Durrrrr exa.minationof the specimenswith a binocular microscope,two were judged unsuitable because The powder data reported by Claringbull of impurities and visible zoning. The others (1951, PDF ffi322) were refined using Cu were given a preliminary analysis by Kar radiation. The cell dimensions obtained are means of an energydispersion SEM system. a 7.51(1), b 9.25(2), c 5.920(5) A, but dis- Material from Can Pey, France (NMC 13540) crepancies between measured and calculated d- was found to contain abundant calcium, but values are substantial for several diffraction the other, from Tsumeb (NMC 13538), proved lines. Similar refinement of the powder data by to be mainly duftite. Guillemin (1956, PDF 14-169) gave a 7.716 Several fragments of the NMC duftite from (8), , 9.178(8), c 5.954(12) A. cuillemin's pattern, which is for duftite with Pb:Ca = 93:7 and Cu:Zn = 96:4, is consideredto be the better of the two, as there are no major devia- tions between measured and calculated d-values (Table 3). In order to obtain cell parameters for end- member duftite, it was asstrmedthat a of Guil- lemin's mineral is slightly high because of the minor substitution of Zn f.ar Cu. In acocordance with the trend in the conichalcite-austinite series, a correction for the Zn substitution was applied by reducing a from 7.716 to 7.71.1 A for the copper end-member which, in this case, has the ratio Pb:Ca = 93:7, Graphical extrapolation to adjust for the calcium content to a of about 7.n4 A for pure duftite. Application of the same kind of correction leads to b 9.182 and c 5.958 A, V 422.1Au for duf- tite. These extrapolations are simplistic in that the Cu-Zn and Pb-Ca substitutions are treated independently, and thus the cell voltrme is only approximate. Other "duftite" specimens Two specimens labeled "duftite" were bor-

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/191/3445757/191.pdf by guest on 01 October 2021 t94 THE CANADIAN MINEMLOGIST

TAELE5. X-RAYPOIIIDER DATA FOR OIJFTITE FROI.I TSI'I'IEB, S.I{.A. (MC 13538) Durrne{oNIcHALcITE Sorm SoruttoN

rest dmas dcalc hhx lest d*, dcalc hhr. The NMC specimen, in which end-member 5 5.03 5.03 0ll t 1.982 1.981 240* 4.59 4.60 020 1.941 1.945 400 duftite contains zones of calcian duftite, also 4.22 4.22 111 4 1.881 1.881 331* I 'r.828 't.826 3.96 3.96 tz0 'I 042' has a narrow rind of calcian duftite with a Cu mainly end-member duftite with narrow bands has been mentioned (Taggart & Foord 1980), containing small amounts of Ca and traces of none of the analyses in the present study ap' Zn (Fig. 1). The bands are too small for proaches this composition. Nevertheless, ex- quantitative analysis, but the broader duftite tensive solid-solution bettween Ca and Pb, and zonescontain < 0.1 wt. Vo CaO and ( 0.1 wt. Zn and Cu in the adelite group seems to be Vo ZnO. common rather than rare. X-ray powder data for duftite from the pol- ished section are given in Table 5. Shrinkage AcrNowlBr:cEMENTS corrections and least-squares refinement were performed as outlined previously. The resultant Specimensfrom. the Royal Ontario l\{useum call volume, 429.7 48, is higher than that ob- were provided through the courtesy of J.A. tained by extrapolation from Guillemin's data. Mandarino; those from the National Mineral The difference may be due to the simplistic Collection were obtained from H.G. Ansell of nature of the extrapolation, the possibility of the Geological Survey of Canada, who also undetected zoning in Guillemin's material or a arranged for some of the SEM studies. The combination of both. writers are also indebted to J.H.G. Laflamme

CaZn austinite

PbCu duftite Ftc. 2. Compdsition plot of intermediate members of the conichalcite- austinite-duftite series. Solid circles: original Tsumeb specimen, NMC 61459; open circles: M 29503; open squares:Dunin-Barkovskaya (1962); solid squares: Guillemin (19-56); solid triangles: Radcliffe & Simmons (t971); open triangle: NMC 13538.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/191/3445757/191.pdf by guest on 01 October 2021 THE ADELITE GROUP OF ARSENATES 195

TABLE6. CELLDIMENSIONS OF THEAUSTINITE-CONICHALCITE.DIJFTITE SERIES

MJneral Cu:Zn Ca:Pb 4(E) u(A) u(i3)rneasu(43)cal Reference c* austini te 0:100 100r0 7.506 (6 ) e.046(6) 5.e32(6) 402.8 Radcliffe & Sfuunons(1971) conlchal ci te I 00:0 I 00:0 7.3e3(7 ) 9.220(r5)5.830(9) 3e7.4 Radcliffe & Slnnons(1971) 69:31 80:20 7.465(6) 9.185(r2) 5.892(5) 404.0 405.5 Analysis I, Table 2 89:I I 60:40 7.46r(5) s.202(r r ) 5.864(7) 402.6 410.9 Table 2 90:.l0 59:41 7.446(7) 9.255(23)5.881(5) 408.5 411.2 Table 2 duftite 95:4 7:93 7.7r6 (8) e.r 78 (8) 5.954(r2) 421.6 427.7 PDFl4-'169, newly refined 100:0 0:I 00 7.734 9.'t82 5.958 423.1 Extrapolated from PDFl4-169 100:0 0:100 7.778(4) 9,207(3) 6.000(5) 42e.7 NMC13538 (Table 5) *Ur"". it that obtained frcm X-ray powderdatai U",.,. ls that obtained by extrapolation frorn the ce'll dimensions of end-menberduftite, conichalcite. and aiitinite.

and J.M. Beaulne of CANMET for technical Perecnn, C., BrnueN, H. & FnoNorr,, C. (1951): assistance,and to E.J. Murray of CANMET for The System ol Mineralogy 2, 7th ed. John Wiley help with the X-ray studies. & Sons, New York. Reocr-rrre, D, & SruuoNs, W.8., Jn. (1971): RrrsnBNcns Austinite: chemical and physical properties in relation to conichalcite, Amer. Mineral. 56, Cr.enrrorur.r,,G.F. (1951): New occurrencesof 1359-1365. duftite. Mineral. Mag, 29, 609-614. Teccanr, J.E., Jn. & Foono, E.E. (1980): Coni- DuNrN-BemovsKAyA,E.A. (1962): Conichalcire chalcite, cuprian austinite, and plumbian con! and staszicite from Lachin-Kahn. Zap. Vses, chalcite from La Plata County, Colorado. Min- Mineral. Obshchest.gl, 146-157(in Russ.). eral, Record 11, 37-38. Gurrr,evrrN,C. (1956): Contribution i la min6ra- logie des ars6niates,phosphates et vanadatesde Received lanuary 1980, revised manuscript accepted cuivre. ,loc. frang. Min6ral. Crist, Bull. 7g,7-95. February 1980.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/18/2/191/3445757/191.pdf by guest on 01 October 2021