American Mineralogist, Volume 70, pages 1044-1049, 1985

Wodginite- and associatedoxide rninerals from the Peerlesspegmatite' PenningtonCountY, South Dakota

P. eeRNf '"'*'wi::{;'il},fii#f ,'ty#:;'xl,"ty;nitoba W. L. Rosnnrs Departmentof Geology South Dakota School of Mines and Technology Rapid City, South Dakota 57701

T. S. Encn ^elip R. CHePIu,c,x Department of Earth Sciences,Unhsersity of Manitoba Winnipeg, Msnitoba, Canada R3T 2N2 Abstract occursin one of the intermediatealbite-rich units of the Peerlesspegmatite, near Keystone, Pennington County, South Dakota. It is associatedwith cassiteritecontaining exsolvedtantalite and , and with . The chemicalcomposition of wodginite varies from (Mnr.nrFeo.uo)(Sn3.ruTa6.55Fef.!.Tio.ou)(Tau.g6Nb1.1a)O.r to Mn3.ee(Sn3.31 Tao.orFef.loTio.or)(Tar.rrNbo.rr)O.2. With decreasingtotal iron, the color of wodginite changesfrom black to pale cinnamon brown. The markedly monoclinic unit cell dimensions (q 9.533-9.552,b ll.47l-11.476, c 5.116-5.123A,p g}.8-.gl.2", v 559.4-561.5A3)suggest a well-orderedstructure. Wodginite and associatedmicrolite seemto be the final precipitatesin a sequence ferrocolumbite+ manganocolumbite+ manganotantalite- wodginite+ microlite. Fractionation progressesin this sequencefrom 0.07 to >0.93 in Tal[a + Nb) and from 0.39to >0.99 in Mn/(Mn * Fe).

Introduction morphology and internal structureis provided by Sheridan (1957). To date, wodginite has been reported from at least 30 et al. major sourceof feldspars, worldwide localities,but until recentlythis has not The Peerless was a during the been recorded in the United States. The first U.S. oc- scrapmica, and amblygonite-montebrasite sheet mica, curren@s were discoveredin the Black Hills of South first half of the 20th century. Punch and byproducts. Dakota in 1979,as describedin the presentpaper, and in -tantaliteand cassiteritewere minor rare exampleof the Herbb no. 2 pegmatite,Virginia in 1981 (Wise and Petrologically,the Peerlessrepresents a pegmatitewhich contains all Li eernf, 1984). a phosphorus-richlithium bound in primary phosphates(particularly as huge quan- The parent pegmatite tities of amblygonite-montebrasite)to the virtual exclusion The Peerless pegmatite near Keystone, Pennington of anhydrous Li-aluminosilicates(cf. Burt and Londonn County, South Dakota is one of the more fractionatedand 1982for the phaserelationships). internally complex pegmatitesof the northern margin of A number of different has been reported from the pegmatitefield of the southern Black Hills. According this pegmatite: plagioclase, qvafiz, varieties, to Sheridan et al. (1957),the pegmatite has an anticlinal -perthiteand microcline are the most abundant shape,with a subhorizontalNW-trending crest flanked by rock-forming minerals; beryl, tourmaline, triphylite, SW- and NE-dipping limbs. The outcrop is about amblygonite-montebrasite,apatite, columbite-tantaliteand 185 x 110 m in size.Three major keels and severalminor cassiteriteare subordinate to a@essoryphases; minor to rolls complicate the apparently -controlledunder- rare mineral speciesinclude garnet, biotite, zircon, spodu- side of the pegmatite,whereas the crestis relatively simple, mene,uraninite, chrysoberyl,tantalian rutile, opal, pyrolu- consistingessentially of two subparallelbulges. Internally, site, goethite,(?), carbonate-apatite, vivianite', fer- the pegmatiteconsists of 7 zones,2 replacementunits and 2 risicklerite, heterosite,libethenite, pseudomalachite, goya- types of fracture-filling units. A detailed descriptionof the zite, autunite, torbernite, siderite,malachite, azurite, loell- 0003-o04x/85/09r0-1044$02.00 t044 ABnni ET AL.: woDcINITE FR,M sourH DAKyTA 1(M5

ingit(?), pyrite, marcasite,stannite and kesterite.During Table 1. The examinedassociations of Nb, Ta, Sn-bearingmin- the present study, wodginite, microlite and tapiolite have erals from the PeerlessPegnratite beenadded to this list. The Peerlesspegmatite is a Na, p, F-enriched rare- Association A: platy columbite (l-6 mmthick, 3-80 cm am$T studdedwith zircon, in cleavelandite: elementpegmatite, with Li, Be and subordinateNb, Ta, Sn samplesA1(ct) to 45(ct). mineralization,and modest enrichmentin Rb and Cs. The ------60-Iffi-inAssociation B: thick tabular columbite- (5 to K/Rb and K/Cs ratios rcach 25.5 and 74Orespectively in maximum di mensi on ) i n coarse-orai ned a I bi te and cleavelandite, with subordinate nuicovite; the K-feldsparsof intermediatezones, 18 and 420 in mus- samplesBl(ct) to 84(ct). covite of intermediate zones, and 13.2 and 3E5 in late, -T20-mlAssociation C: coarse-grained anhedral cassiterite (5 to slightly Li-enriched muscovite of the central parts of the with exsolved columbite-tantalite and taDio- pegmatite Iite, in cleavelandite+ muscoviteadjacent to (0.35 wt.% LirO). Beryl also shows increased massivequartz; samples contentsof LirO (< 1.10wt.o/o) and CsrO (< 1.05wt.%). Cl(c) with exsolvedCl (ct) C2(c) with exsolvedC2(ct) Paragenetic relationships C3(c) with exsolvedC3(t) of wodginite C4(c) with exsolvedC4(t) Wodginite was found in the cleavelanditefringe of an Association D: wodginite (divergent columnaraggregate albitic unit exposedin the northeastern,partly overhanging 50 mmlong) with inclusions and/or exsolutionsof cassiterite,'landite microlite and tapiolite, in cleave- wall of the main pegmatitequarry, very close to the E-8, + muscovite adjacent to massivequartz; sectionline ofSheridan et al. (l957,plate 4). The cleavelan- samDI es dite fringe which containsintergrown Dl(w) black-brownwith overgrowthof Dl(t), muscoviteis located and D](c) with exsolvedD](ct) along the contact of the albitic unit with an underllng D2(w) brown D3(w) pale brownw'ith massof qvaftz. SectionE-E' in Sheridanet al. (1957,plate D3(c) and D3(m) 6) indicates that the present exposure correspondsto a A, B, C, D - mineral associations;l, 2, 3,.., - samDles segmentof zone 6b overlain within eachmineral association;ct - columbite-tantalite. by the 3rd intermediate c.- cassiterite, w - wodginite, t - tapiolite, m - micro- cleavelandite+ quartz zone 5, as designatedby theseau- n f,e. thors. Becauseof the relative abundanceof columbite-tantalite and cassiteritein the wodginite-bearingalbitic unit, repre- procedure; becauseof the lack of material, it was X-rayed in a sentativespecimens of theseminerals were collected over Gandolfi camera and the film data were corrected for shrinkage. the accessiblewidth of this unit, and examinedin order to In all cases,the program cenrr (Appleman and Evans, 1973)was establishthe generalparagenetic and geochemicalenviron- usedfor unit cell refinement. ment in which the wodginite occurs.The different mineral In the heating experiments, separatefragments 0.5 to 2 mm in associationsare listed in Table 1, letter-codedin the se- size were extracted from the samples and were heated in air at 1000'C for 16 hours. Heating quence of their occurrencefrom inside the albitic unit relatively coarse-grainedmaterial toward the massivequartz zone. minimizesoxidation of Fe2* to sucha degreethat unit cell dimen- sions of columbites-tantalitesheated in air and in controlled at- Experimental methods mosphere (CO1CO2: 2.51D are statistically identical (unpubl. data of eernf and Turnock). All chemicalanalyses were done with an MAC 5 electronmi- croprobeoperating in both wavelength-dispersive(WD) and Mineralogy energy-dispersive(ED) modes.Standards used were cassiterite (SnLc), chromite (FeKa), sphene (TiKc), manganotantaliteWodginite (MnKc, TaLa, Md), BarNaNbrO* and CaNbrO" (NbLa). Con- The divergentcluster of subhedraland somewhatskele- ditions of analysis were: acceleratingpotentials of 20, 15 kV, samplecurrents of 40 nA (WD) and 5 nA (ED) measuredon brass tal wodginite crystals is black at the point of spreading, (WD) and ZnS (ED), count times of l0 s (WD) and 200 live grading into medium-brown and turning pale cinnamon- seconds(ED). Wavelengthdispersive spectral data were reduced brown at the diverging crystal terminations. The black with the program EMnlDR vrr (Rucklidge Gasparrini, 1969). point of the cluster contains cassiteritegrains with micro- Energy-dispersivespectra were collected with a xsvEx Model 7000 scopic tantalite inclusions, and microgranular tapiolite ED spectrometer and were reduced with rEvE ( software utilizing along contacts of cassiteritewith wodginite. Intermediate the program MAcrc v (Colby, 1980).Peak overlap problems en- parts of the wodginite clusterare not associatedwith other countered during analysis of ED spectra were resolved by strip- phases;however, the divergingwodginite terminationscon- ping techniquesinvolving library spectra. tain exsolvedcassiterite, and euhedralcrystals of pale gray Most unit cell dimensionswere calculatedfrom X-ray powder microlite along wodginitecontacts with . diffraction data obtained with Philips X-ray diffractometers using In general, the wodginite Ni-filtered or graphite-monochromatedCuKa radiation (,l': composition is close to the ideal formula MnSnTarOr, particularly 1.541SA)and scanningspoeds of U4 to U2" 2llmin. A minimum in the diverging of 10 and a maximum of 33 reflections measuredbetween 10. and pale-brown terminations (associationD, Table 1, Fig. 1). 7O"20 were used in least-squaresrefinement of the data. Annealed AnalysesDlw and D3w are among the most Sn-rich com- CaF, (a : 5.46204)was used as an internal calibration standard. positions found in wodginites(unpubl. data of T.S.E. and Wodginite sampleD(w) (Table l) was the only exceptionto this r.e.;. ln the (Nb, Ta)or.r-{Fe, Mn)G{Sn, Ti)o, diagram, 1046 CnnN{ ET AL.: woDcINITE FRqM sourH DAKoTA

Fe Ta2O6 Mn Ta ^Oe wodginite compositionsplot very closeto the ideal substi- I O- (Fe, Mn)2+ 2,(Nb,Ta)5*+3(Sn, Ti)a* (Fig. D2(w) | tution trend + 2), which joins ideal columbite-tantalitewith the (Sn' Ti) C4(c) corner. However, this plot is somewhat unrealistic for wodginite becausewodginite includes minor Fe3* with Fe2*. Site assignmentswere made according to the present ::r{:_ of the crystal chemistry of wodginite (Fer- understanding "::'--2 guson et al. 1976; Ercit, Grnf and Hawthorne, in prep.) "'9L-1 ind its recentlyexpanded compositional variability (eernf and Ercit, 1985).Mn2+ was assignedto the A-site, all Nb and Ta : (8-Nb) were assignedto the B-site and Ti, Sn and excessTa from the B-sitecalculations were assigned to z + the C-site.Fe2+ :Fe3* was calculatedfrom the total iron of F analysisby assumingall iron in the A-site to be ferrousand all iron in the C-site to be ferric, in analogy to the results of wet chemicalanalyses of other samples(von Knorring et al. 1969)and on site chargeand sizeconsiderations (Ferguson et al. 1976\.In such calculationsit is important to consider Fe Nb2O6 Mn Nb2oo Mn/(Mn+Fe) the distribution of cation site vacancies(Graham and I o 10 Thornber, 1974).Yacancres are incorporated as part of an attempt to achievecharge balance,necessitated by excess Fig. l. Compositions of the examined minerals in the positive chargeintroduced by Sna+- Tas+ substitution at columbite-tantalite (-tapiolite) quddrilateral. Dots---rolumbite- the C-site. As such, vacanciesshould be preferentially,al- tantalite; horizontal diamonds-wodginite; upright diamonds- not necessarilyexclusively, incorporated into the tapiolite; triangles----cassiterite.Dashed lines connect coexisting though valencerequirements minerals; thin lines encircle individual mineral associations adjacentA-site, to satiatelocal bond characterizedin Table 1; the arrow shows the general frac- (Ercit, eern! and Hawthorne, in prep.)' In calculations tionation trend as describedin the text. wherethe A-site could not accommodateall vacancies,the

(Nb,Ta)O2.5

(Nb,Ta) O 2.5 e,Mn)(Nb,Ta)rOa

(Fe,Mn)O

v/ (Fe,Mn)O

(sn,Ti)o2 10 20 10

Fig. 2. Composirionsof the examinedminerals in the (Sn, Ti)Or-{Nb, Ta)Or.r{Fe, Mn)O Fiangle. Symbolsas in Fig 1. Dashed +*3Ra + linesmark the R2* 1 2ft5 substitutiontrend in columbite+ypephases. Crnri ET AL.: woDGINITE FRaM sourH DAKqTA tM1

remaining vacancieswere assumedto be located at the volving a decreasein total Fe with decreasingintensity of C-site.Following the aboveprocedure, the formulae of the color. Variations in Ti appeatto be erratic, possiblyinflu- analyzedwodginites can be written enced by the relatively large analytical error at the low concentrationlevels encountered.The Tal(Ta * Nb) ratio (Mn3.l5Fe3:oXSnr.ruTio D(w) ouFe!.!.Taorr[Ta" r6Nbr.14)O32seems to be rather stable, and the Sn/(Ta + Nb) ratio (although D{w)c (Mnl.!.[Snr."rFel]oTar.o/Tar..oNbo.ro)O., changeserratically it may be significant that it increasesin the crystal terminations coexisting with dis- D2(w)m (Mnl.!"[Snr.rrFel.]rTao.ru)(Ta7.2?Nbo 73)O32 crete cassiteritegrains or containing possiblyexsolved cas- D3(w) (Mnlj,r[Snr.rrTio.orFef.]oTao.n.[Tar.r rNbo.rr)O' siterite). Unit cell dimensionsof all color varieties show the f Changesin chromophoreconcentrations throughout the angle deviating appreciablyfrom 90" (Table 3), and they color gradation describedabove are relatively small, in- changeonly slightly after heating at 1(n0'C/16 hrs. in air.

Table 2. Electron microprobe analysesof the Nb, Ta, Sn-bearingminerals from the PeerlessPegnatite

Sample Ta^0. lla^0. Ti02 Sn0, Fer0, teu Mn0 Total number za aa

Al(ct) 9.7 70.0 0.2 0.0l 8.2 ll.8 99.9t A2( ct) 9.5 70.2 0.I 0.05 8.02 ll.9 99.77 A3(ct) 3?.1 49.8 0.4 8.6 9.9 100.8 A4(ct) ll.1 69.8 0.4 8.0 12.7 102.0 A5(ct) 21.0 56.5 0.6 12.3 8.0 t0l.4 Bi(ct) 49.6 0.3 6.0 11.2 'l00.I 00.4 82(ct) 4 60. 23.5 0.3 12.7 'l00.20 B3(ct) 61.8 0.'] 0.2 2.8 13.0 84(ct) 62.0 2l.0 0.2 0.4 ?.0 13.9 99.5 cl (ct) s9.4 tt. I 0.6 0.9'I 6.4 9.2 99.? c2(ct) 57.? 0.4 .5 10.8 'I+,o 98.9 Dl(ct) 72.0 |.3 0.6 0.5 3.2 t.9 99.5 cl(c) Lt 0.7 0.l 97.7 0.3 0.03 99.93 c2(c) 2.9 0.5 0.06 94.7 0.4 98.56 c3(c) 2.5 0.7 0.1 96.7 0.2 100.2 ca(c) 4.2 0.3 94.9 0.8 100.2 Dl(c) 1l.7 0.7 0.1 85.0 0.3 99.2 D3(c) 0.6 99.I 99.7 c3(t) 75.5 8.7 0.8 2.7 12.8 0.3 100.8 c4(t) 71.7 |.5 0.3 1.2 13.8 0.9 99.4 D](t) 80.9 0.2 2.1 13.3 0.6 l0t.3 Dl(w) 62.9 5.8 0.? 18.3 0.7 l.l 9.4 98.5 D2(w)core 69.2 3.5 0.0 15.2 0.3 0.0 10.5 98.6 D2(w)margin 69.0 0.0 15.7 0.5 0.0 't0.910.4 99.2 D3(w) 64.9 0.2 19.2 0.3 0.0 99.5

5amp1e C+ 6+ -.4+ ^4+ -2+ numDer Nb- ll )n Fe"' l.ln TotaI '1 Al( ct) 0.615 7.383 0.035 0.001 - I .600 2.332 1.966 A2( ct) 0.602 7.401 0.035 0.005 - I .560 2.351 ll .954 43(ct) 2.222 5.731 0.088 - 1.831 2.134 11 .994 A4(ct) 0.693 7.248 0.069 - I .537 2.471 12.018 A5(ct) 1.596 0.I10 - 2.515 I .657 12.126 Bl(ct) 3.750 4.186 0.063 - 1.395 2.638 12.032 82(ct) 4.854 3.140 0.035 - 0.766 3.179 11.976 83(ct) 4.987 2.992 0.022 0.024 - 0.695 3.267 ir.986 84(ct) 5.061 2.850 0.045 0.048 - 0.502 3.534 1?.C40 C1(ct) 4.798 3.048 0.134 0.107 - 1.590 2.314 II .991 cz(ct) 4.598 3.261 0.089 0.177 - 2.670 1.152 11.946 Dl( ct) 6.20'] I.618 0.143 0.063 - 0.848 3.192 r2 .065 cl(c) 0.015 0.016 0.004 I .951 - 0.013 0.001 1.999 c2(c) 0.040 0.0t2 - 0.002 'II .925 0.017 't.992I .996 c3(c) 0.034 0.016 0.004 .930 - 0.008 ca(c) 0.057 0.007 I .903 - 0.034 2.001 Dl(c) 0.r63 0.016 0.004 1.736 - 0.060 0.013 1.992 D3(c) 0.008 I .990 I .998 c3(t) 3.?64 0.625 0.096 0.I 7] - 1.702 0.040 5.899 c4(t) 3.t0t 0.827 0.036 0.076 - 1.835 0.']2] 5.996 0r(t) 3.599 0.3ll 0.025 0.137 - 1.820 0.083 5.974 Dl(w) 7.408 l.'t36 0.065 3.160 0.228 0.398 3.448 I 5.844 D2(w)core 8.323 0.700 0.000 2.680 0.100 0.000 3.933 I 5.736 D2(w)marg'in 8.227 0.733 0.000 2.745 0.r 65 0.000 3.862 15.732 D3(w) 7.6?7 0.821 0.065 3.308 0.098 0.000 3.990 15. 907

Atomiccontents are basedon 24, 4, 12 and32 oxygensfor columbite-tantalite (ct), cass'iterite(c), tapiolite (t) andwodginite (w), respectively. annttf ET AL.: woDcINITE FRaM sourH DAKoTA

This behavior suggeststhat the natural material is well Table 3. Unit cell dimensions of columbite-tantalites and wodgin- ordered,with cation distributionsclose to the fully ordered ites from the PecrlessPegmatite formulaepresented above. sample u,R c,R B v,fl3 numDer a.R Columbite-tantalite Natural Columbite-tantalitecrystals appear in two main forms: A3(ct) 14.295(2)5.7?9(1 ) s.ll3(2) - 418.72(121 thin but sizeableplates within the albitic unit, and thick A4(ct) 14.311(2) 5.742(l) 5.r010) - 4r9.16(8) A5(ct) 14.258(2)5.731 (l ) 5.086(I ) - 415.59(1r ) tabular to stumpy crystals closer to the outer margin of 82(ct) 14.300(3)5.741(l) 5.r24( I ) - 420.6102) this unit (associationsA and B, Table 1). In both types of 83(ct) l4.323(4)5.745(2 ) s.090(3) - 4r8.83(2r) - 4?0.39n2) crystals,the mineral appearshomogeneous, having no sig- 84(ct) 14.322(3)5.743(2) 5.r250) Dl(w)' 9.s52(r2)il.475(6) 5.r23(3)gOlso (s) s61.5(7) nificant chemicalzoning, nor containing any inclusionsor D2(w) 9.533(l)11.471(l) 5.il7(r)9r:10'(0.6) 559.5(l) exsolution lamellae of other oxide minerals. Samples A D3(w) 9.533(2)11.471 (2) 5.115(l)9l']2'(0.9) 559.4(l) have the compositionof ferrocolumbiteto manganocolum-

bite, samples B straddle the manganocolumbite- A3(ct) 14.320(4) 5.741(21 5.065(I ) 416.37(14) manganotantaliteboundary (Figs. t and2, Table 2). A4(ct) 14.352(2)5.745(l ) 5.068(r ) 4r7.89(7) A5(ct) l4.3ll(3) 5.738(l) s.06s(1 ) 415.9501) The unit cell dimensionsof both A and B typcs indicate 82(ct) 14.395(4)5.754(l ) 5.08r(2) 420.84(r6 ) considerabledegrees of (Fe, Mn){Nb, Ta) disorder. Heat- 83(ct) 14.381(4) 5.7s0(2) 5.076(I ) 419.7r(r5) 84(ct) 14.396(4) 5.757(l) 5.085(2 ) 421.48(15) ing at 1fi)0'C in air for 16 hrs. leads to near complete Dl(w) ordering of the structure,in accord with the almost ideal D2(w) 9.526(?1 11.47412) 5.il60) 91:r2:il.2)559.10) 9.531(3)11.46s(2) 5.I180)91'13 0.21 559.2(2) stoichiometryand low content of quadrivalentcations (Fig. D3(w) 3, Table 3). The only other types of columbite-tantalitefound in the Gandolfi camera courseof the presentstudy are associatedwith cassiterite.

Cassiterite apparent exsolution product, but only in cassiteritewhich Cassiteriteis the main in the cleavelandite doesnot carry any columbite-tantalitephase. + muscovitefringe of the albitic unit (associationC, Table 1). Its composition is highly variable,containing a total of Tapiolite l.7l to L4.17wt.% of Nb, Ta, Fe and Mn oxides(Table 2). Microscopic crystals of tapiolite occur along the Within the limits of experimentalerror, all compositions cassiterite-wodginitecontacts and on the surfaces of appear to fall on the (Fe, Mn)2+ + 2{Nb, Ta)5++3(Sn' wodginite crystalsin associationD, and as rounded blebs Ti)a* trend (Fig. 2). in cassiteriteC. Tapiolite C is probably formed by exsolu- Microscopic grains of ferrotantalite and manganotanta- tion and recrystallization,whereas primary crystallization lite are observeddispersed along fracturesin cassiteriteor following the precipitation of wodginite is evidently the within the cassiteritecrystals, texturally resemblingexsolu- origin of associationD. Tapiolite was recognizedby its tion bodies (Table 2, Fig. 1). Tapiolite is also found as an optical properties and faint diffraction lines in some cas- siterite X-ray patterns, and confirmed by electron micro- probe analysis (Table 2). All three analyzedgrains contain little Mn and are relativelyenriched in Nb (Fig. 1).

Microlite Tiny octahedraof pale-greymicrolite are rarely found on the surfaceof wodginite D3w. Microlite was identified by X-ray diffraction but was not found in polished sections, thus its chemical composition could not be established. However,it is suggestedthat the Tal(Ta + Nb) ratio of this microlite is the sameor higher than that of the associated wodginite, as is commonly found in at other localities (e.g.,Vorma and Siivola, 1967 and Grice et al. r972). 14.10 14.20 14.30 . 14.40 a,A Parageneticsnd geochemicalconsiderations Fig. 3. Unit cell dimensionsof columbite-tantalitein the a - c plot modified from eernf and Turnock (1971).All data basedon As is evidentfrom TableI and Figure1, a distinctmin- the ordered supercell. Unit cell dimensions of the structural end eral successionand geochemicaltrend can be recognized membersafter eernf and Ercit (1985).Data for natural samples from the inner partsof the albitic unit towardits margin (with sample numbers) linked with values after heating at alongthe massivequartz. A ferrocolumbite+manganocol- 1000"C/16hrs. in air (unmarked). umbite+ manganotantalitesequence is followedby cas- Anattf ET AL.: woDcrNITE FR2M sourH DAK|TA 1049 siterite and (probably minor) wodginite + microlite. This p. 19).The mineralis underfurther study by T.S.E.and mineral successionis marked by an extensiveNb--Ta frac- E.E.F. tionation covering 85% of the total Tal(Ta Nb) + range, References and a less spectacularbut distinct Fe-Mn fractionation in the Nb, Ta-rich minerals. The extent of Ta-Nb frac- Anderson, A. J. (1983) The geochemistry,mineralogy and pet- rology of the Lake pegmatite field, central Manitoba. tionation displayed here in a single unit (of a pegmatite Cross M.Sc.thesis, University of Manitoba, Winnipeg. consistingof 11 units) is rarely documented from complete Appleman,D. E. and Evans,H. T., Jr. (1973)Job 9214: indexing border- core+ replacementsequences of other pegl'a- and least-squaresrefinement of powder diffraction data. U.S. tites, or from entire pegmatite groups (e.g.,eernj' et al., Geological Survey, Computer Contributions, 20,; NTIS Docu- 1981b;Anderson, 1983; eern! and Ercit, 1985). mentPB2-16188. With regard to the exsolution phenomena, cassiter- Burt, D. M. and London, D. (1982)Subsolidus equilibria- Miner- ite + tapiolite pairs show erratic and generally restricted alogical Association of Canada Short Course Handbook, 8, partitioning of Fe, Mn, Nb and Ta. [n contrast,columbite 329-346. exsolvedfrom cassiteriteis considerablyenriched in Mn, eernf, P. and Ercit, T. S. (19E5)Some reoent advancesin the and in most casesalso in Nb (samplesDl, C2). The Ta- mineralogy and geochemistry of Nb and Ta in rare-elernent granitic pegnatites. press. enrichmentshown by tantalite Cl(ct) relativeto its cassiter- Bulletin de Min6ralogie, 109,in eernf, P., Paul, B. J., Hawthorng F. C. and Chapman,R. (l98la) ite host is surprising,in view of the generalpreference of A niobian rutilcdisordercd columbite intergrowth from the Nb for the columbite (e.g., structure Weitzel, 1976; eernil Huron Claim pegmatite, southeastern Manitoba. Canadian et al., 1981a).From the distribution of compositions in Mineralogist,19, 541-548. Figure I it appearsthat the assemblageD could have ap- eernf, P., Trueman,D. L., Zehlke, D. V., Goad, B. E. and Paul, proachedequilibrium much closerthan any of the mineral B. J. (l98lb) The Cat Lake-WinnipegRiver and the Wekusko pairs of assemblageC. Lake pegmatite fields, Manitoba. Manitoba Mineral Resources Another point of interest is the precipitation of wodgin- Dvision, EconomicGeology Rept., ER8G1. ite in the cassiterite-richmargins of the albitic unit. This is Grng, P.and Turnock, A. C. (1971)- minerals undoubtedly the consequenceof oversaturation of the from granitic pegmatitesat Greer Lake, southeasternManitoba. Canadian Mineralogist, lO, 755-772. parent environment with tin, but the reasons for crys- Colby, J. W. (1980)MAGIC V-a computer program for quanti- tallization of wodginite rather , than staringite,tho- tative electron-excited energy dispersive analysis. In: reaulite + manganotantalite or cassiterite + man- QUANTEX-Ray Instruction Manual, KEVEX corporation, ganotantalite are not known. Detailed analysisof natural FosterCity. assemblagesbearing these species,and extensiveexperi- Ferguson,R. B., Hawthorne, F. C. and Grice, J. D. (1976)The mental studiesare requiredto clarify this question. crystal structures of tantalite, ixiolite and wodginite from Bernic Lake, Manitoba. IL Wodginite. Canadian Mineralogist, 14, Acknowledgments 550-560. This studywas supported by theNSERC of CanadaOperating Grice, J. D., eernf, P. and Ferguson,R. B. (1972)The Tanco- GrantA-7948, and by theDEMR of CanadaResearch Agreement pegmatite at Bemic Lake, Manitoba. II. wodginite, tantalite, 29+1983,grant€d to P. eernf. We are indebtedto Dr. F. C. pseudo-ixioliteand relatedminerals. Canadian Mineralogist, 11, Hawthorneand Ms. K. J. Olsonfor helpfuldiscussions, help in ffi-&2. experimentalwork and critical readingof the manuscript.Thor- v. Knorring O., Sahama,Th. G. and Lchtinen, M. (1969)Ferroan ough reviewsby Drs. M. Ross,D. E. Voigt and E. E. Foord wodginite from Ankole, southwest Uganda. Bulletin of the Geo- considerablyimproved the presentation. logical Societyof Finland, 41,6#9. Rucklidge,J. and Gasparrini, E. (1959)Electron microprobe ana- Note addedin press lytical data reduction (EMPADR VII). D€pt. Geology,Univer- sity ofToronto. Mr. Richard Schoonerof Woodstock,CT found wodgin- Sheridan,D. M., Stephens,H. G., Staata M. H. and Norton, J. J. ite in 1981or 1982in the Strickland Quarry, Connecticut (1957)Geology and beryl deposits of the Peerlesspegmatite, pegmatite. provided He us with severalcrystals, associated Pennington County, South Dakota. U.S. Geological Survey with manganotantalite,that proved to be Ti-enriched in ProfessionalP aper, 297- A. central parts and Ti-poor in (the margins): MnO 11.0 Turnock, A. C. (1966)Synthetic wodginite, tapiolite and tantalite. (10.6), FerO3 0.8(1.0),TiO, 0.9(0.5),SnO, t5.3(16.4), Canadian Mineralogist, 8, 451470. Nb2O5 4.4(3.8), TarO, 66.1(66.0),total 98.6(98.2) Vorma, A. and Siivola, J. (196T Sukulaite-TarSnrOr-and wodginite as inclusions in cassiterite in the granite pegmatite in wt.Yo. Core Mnn.or(Snr.uoTao..rTio. roFef .l rlr..rn(Tar.,n Nbo.rr)rr.oo Orr, margins Mnr.rr(Snr.ruTao.rrFefl.l, Sukula"Tammela, in S.W. Finland. Bulletin de la Commission 229, 173-187. Tio.ro)"rr, (Tar.r." Nbo.74L8.ooo.r.Unit cell dimensions G6ologiquede Finlande, Weitzel, H. (1976) Kristallstrukturverfeinerung von Wolframitcn (single-crystaldiffractometer) are a 9.522(l), b 11.467(2), c und Columbiten. Zeitschrift fur Kristallographie, 1,14,23U258. 5.115(1)4, 9t.l.t8(2)". "Monoclinic P Data on ixiolite',,re- Wise, M. A. and Grnf, P. (1984)First U.S. occunenoeof wodgin- cently recognizedto be disordered wodginite, from Ala- ite from Powhatan County, Virginia. American Mineralogist, bama were presentedby Foord et al. (Foord, E.E., Allen, 69,807-809. M.S., and Heyl, A.V.: Internat. Symposium"Mineralogy in Manuscriptreceiued, December 27, 1983; the Earth Sciencesand in Industry", Toulouse 1984,Abstr. acceptedforpublication, Februmy 19, 1985.