LN

Canadian Mineralogist Vol. 30, pp. 1n-136 (1993)

A CRYSTAL.CHEMICALINVESTIGATION OFALPINE GADOLINITE

FRANCESCODEMARTIN Istinto di ChimicaStrumtristica Inorganica" Universit degli Studi, Via G. Venezian21, I-20133 Milan' Italy

TULLIOPILATI CentroCNR per Io Studiodelle Relazioni fra Strunurae ReattivitChimica, via Golgi 19,I-20133 Milan' Italy

VALERIADIELLA Centro CNRdi Sndio per la Stratigrafia e Petrografiadelle AIpi Centrali, via Bonicelli 23, I-20133Milan' Italy

PAOLO GENTILE AND CARLO M. GRAMACCIOLI Dipanimentodi ScienzedellaTerra, Ilniversit degli Studi,via Bonicelli 23, I-20133Milnn' Italy

ABSTRACI

Gadolinite-(Y) specimensfrom variouslocalities in the Alps havebeen examined by electronmicroprobe and single-crystal X-ray diffraction. tn generat,dysprosium is the most abundantrare-earth, although a few samplescontain approximately equal ulnount,of Dy undYb-,andin oneinstance, Gdpredominates.Incontrasttomanynon-Alpineoccunences, mostof these specimens show only lirnited amountsof the lighter REE.There is an almostconstant presence of calcium (up to 4 wt7o.CaO' and.possibly twice thai amountfor morequestiorible samples;;iron is often markedlydeficient with respectto the tleqretlcal formula, and in ar leastone case (Glogstafelberg), the materialshould more properly be ialled hingganite-(Y)(4.0 wrToFeO). In somespecimens, a silnificant substituiionof S fJi Be (up to about4 .Z wtUoUrOll canbededuced-from crystal-structure data, on the basisof linear inteipolation of the measuredBe-O''6ond lengfhswith reip".t to other gadolinite-groupminerals. This substitutionis more exteisive for specimenshigh in Ca and low in Fe, and which thereforegrade toward datolite. No evidencefor replacementof Si by B hasbeen iound. Minor amountsof thorium (up to 0.4 wtToThO2)commonly are present' and uranium(0.3 wtVoUO) was found in one specimen.As for xenotimeand monazite,the behaviorbf Y is not uniquely determinedby the ionic radius,some specimensbeing especiallyemiched in this elementwith respectto the middle-heavyrare earths(up to 4 I .5 wt%oY 2O) . Keywords:gadolinite, hingganite,rare earths,yttrium, beryllium, boron, pegmatite,fissure, Alps, crystal-structureanalysis' electron-microprobeanalysis.

SOMMAIRE

Nous avonscaract6ris6 plusieurs fchantillons de gadolinite-(Y)provenant de localit6salpines par microsondedlectronique et plus desterres rares, quoique certains par diffraction X sur cristal unique.C'est en g6n6ralle dysprosiumqui est la lbol9anre 6chantillonscontiennent une proporrion 6quiialente OeOy et de Yb, et quoique le Gd pr6dominedals y1-{es 6chantillons' Contrairementi plusieurs provenantd'ailleun, li plupart desdchantillons ne.contiennent que de faibles quantit6sdes terresiares l6gdris. p calcium"*..pi". est pidsent dans presque tous leicas, en quantitdsallantjusqu'd 4Vode CaO, etpouvantatteindre le doublede ceci dans certains 6chantillons moins bien caract6ris6s. Le fei estfortement ddfcitair,e pqq rypport ela formuleid6ale; dffi"^ffi;i.s |1n6iei"L$'i"1i;;6;F;ifiil;a;64;rii6fre o€G appetonineganite-ffi @.MoF{'par pids). Danscerains 6chanrillons,une proponion importante du Be est remptac6e par le B (usqu'l environ4.2Vo deB2O3par poids), d'aprbs les donn6es obtenuessur la structurecrlstaitine de cetteespbce, d la lumibre d'une interpolationdes longueurs Be-O mesur6espour certains pour de nos &hantillons, par rappor A d'autres min6rauxdu groupede la gadolinite.Cette substitutionest plus r6pandrre les echantillonsriches en Ca et pauwesen Fe, et donc ceux qui montrentune tendancevers la compositionde la datolite.Nous ne trouvonsaucun indice d'un remplacementdu Si par le B. De faibles quanritdsde Th (usqu'i 0.47ode ThO2par poids) sont assez le courantes,et1.3vo de UO2 esipr6sentdans un de nos 6chantillons.Comme dans le cas du x6notimeet de la monazite, en comportementde I'yttrium ne semblepas ddpendre uniquement du rayonionique; certains 6chantillons sont fonement enrichis Y par rapportaux terres fares moyennes et lourdescusqu'h 41.57o YzO:). (rraduit parla R6daction)

Mots-cl6s:gadolinite, terres rares, ynrium, b6ryllium, bore,pegmatite granitique, fissure, Alpes, 6bauche de la structurecristalline' analysei la microsonde6lectronique.

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INTRODUcnoN othertypes of substitutionmay not be excludeda priort. Among these,for instance,the presenceof additional Whereasgadolinite has beenknown for nearly two beryllium replacingsilicon hasbeen postulated by some centuries,its discoveryas a fissuremineral in theAlpine authors,on the groundsof infrared absorptionspectra reglon took placemore recently(parker et at. li40). (Aleksandrovaet al. 1966); similarly, the presenceof Becauseof its geologically"young,, age, gadolinite four OH groupssubstituting for SiOa,as in hydrogarneq from the Alps is very different from that of most other is anotherpossibility; furthermore,significant amounts occurences;it commonly is referredto as .,noble,' ofP and F [in view ofthe isostructuralrelationship to gadolinite,as the crystalsare sharp and transparent, their herderiteCaBePOa@,Ott) and its groupl or of Bi [asin color is generallypale greenor blue-green,reminiscent minasgeraisite(Y,Bi)2CaBqSirOlsl also may be pre- of beryl or somebluish varietiesof titanite, with which sent. suchcrystals of gadolinitemay easilybe confused. As is the case for monaziteand xenotime"there are CHEMICAL ANALYSIS also occurrencesin granitic pegmatites.Most of these havebeen discovered in Val Yigezzo(Ossola) (Mattioli 1977, 1978, Turconi 1982, Albertini 1988); in the Electron-microprobeanalyses were performed on eastemAlps, occurences are known at the so-called polishedgrain-mounts, using the wavelength-dispersion ARL-SEMQ instrument "Plattenbri,iche''in the Rauris Valley (Meixner 1976) of the Italian National Re- searchCouncil (C.N.R.) and in the Markogel pegmatite near Villach (G. at the Centrodi Studi per la Niedermayr,pers. comm., 1990). Stratigrafiae la Petrografiadelle Alpi Centrali,Milan. Most of the scientificwork on Alpine gadolinitehas To determinethe contentof Si, Ca,Fe andU, a series been concernedwith its mere identification. In a few ofnaturaland synthetic standards was employed. Forthe cases,optical and morphological data and X-ray powder rare earths, Y and Th, synthetic lithium metaborate glasses patternsare given; however, no structurerefinement has were preparedas specifiedin our contributions been carried out so far, and accuratevalues for the on Alpine monaziteand xenotime (Mannucci et al. 1986, unit-cell parametersare lacking in the literature.Simi- Demarttnet al. l99l a,b). Theaccelerating potential was larly, recentresults of quantitativechemical analyses, 20 kV, the samplecurrent (on brass)0.01 pA, andthe including the distribution of the rare-earthelemenrs MAGIC IV correctionprocedure was applied(Colby (REQ, ue not available. 1968, with modifications).In all the sampleshere The unusualperfection and "freshness"of the crys- examined,the concentrationsof Tb, Ho, Mg, Sc,P, S, tals, which are almost unique in nature,make th;m Sr, 84 Na, F, andAl arebelow the limits of detectionof ideally suitedfor chemicalanalysis and a studyby X-ray our instrument(about 0.1 wt%o);forTmand Lu, owing diffraction. Advanced metamictizationand leaching to interferencefrom Dy, the limit is higher (about 0.4 accompaniedby oxidation, commonly observedin wtVo). non-Alpinegadolinite, might leadto grosslyerroneous Besidesthe interferencesamong the REd theanalyti- conclusionsabout the crystalchemistry of this mineral. cal line of dysprosium@yfct) is too closeto a line of For instance,a recentunpublished investigation carried iron (FeKa), so that on oneside the backgroundwas too out by our group on the glassy core of crystals from high, leadingto unacceptablylow valuesfor the DyrO. Baveno(which are much older than Alpine specimens, content. This interferencehas been accountedfor by thoughfound in the samevicinity) showedthat thereis measuringthe background ofDylcr on oneside only. an almost completeseries of compositionsbetween Our data pertain to material from fwelve localities "true" gadoliniteand an amorphousmass of hvdrated (Table 1). The variation in oxide percentagesreported iron oxideand silica. includesboth statisticaluncertainty in countingand Also, crystallographicdata of good quality are rare actual compositionalvariation in the sample,since for on this species(Miyawaki et al. 1984).They can be most specimensthe reportedvalues are the averageof importantin view ofthe existenceofextensive solid-so- sevenanalyses, performed on different points. For the lution with other minerals of the same goup, e.g. specimensfrom Hopffeldbodenand Triolet, owing to hingganite (Y,Yb)2BqSi2O8(OH)2(Semenov er a/. lack of homogeneityof the samplesand also to the 1963,Voloshin et al. 1983,Yakubovich et al. 1983\or impossibilityofrepeating the measurements in optimum even datolire CaBSiO4(OH), calcium-gadolinite, conditions,the resultsare less accurate than for theother homilite Ca2FeBrSi2O,o(Miyawaki et al. 1985),etc. specimens.For example, the Y contentis surelytoo high, Thesesolid solutions commonly involve compositional and this also explainsthe unusuallyhigh value for the variationinvolving light elementssuch as Be or B, and MelSi ratio for the specimenfrom Hopffeldboden(see preselceof water.For this reason,electron-micronrobe below). data must be supplementedby other data in order to Unfortunately,t}re amounts of somelighter elements establishthe chemicalcomposition exactlv. could not be determinedby our microprobeanalysis; Besidesthese well-known schemesoi substitution among these, boron and beryllium are particularly (Ito l967,Ito & Hafner 1974,Miyawaki et al. l9g4), important for gadolinite. This lack of data can be

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TATI,E 1. ANAIITICA! DATE ON AIPIT'E GAI'OTJIISITE obviatedusing resultsfrom crystal-structurerefinement (seebelow), which indicate common partial substitution (5) (6) se!,re (1) (2) (3) ({) presenceof a realisticamount of boron La2O3 0.2(r) of B for Be. The GzO: - 0.3 ( 1) 0.9 (? ) 0.4 (3 ) in the Glogstafelberg sample was confirmed by a Pr2o3 O.2l2l semiquantitativemicroprobe analysis performed with a Nd2o3 0.3(3) O.112) 1.4(9) 0.9(5) 0.1(1) O.2l4l XL SEM equippedwith an EDAX energy-dispersion mzo: 0.4(4) 0.?(2) 1.0(5) X.2(6) 0.3(2) 0.2(3) dzo3 1.4(6) 1.8(6) 1.8(6) 3.s(12) 1.4(s) r.x(14) sDectromeEr. Dyzo: 4.1(1) 4.0(1) 3.9(4) 6.6(6) 4.s(5) 4.0(9) Even for the most boron-rich specimens,the atomic E!2o3 3.4(3t 3.4(3)' 3.0(2) 3.3(4) 3.2(5) 3.?(8) ratro Melsievaluatedfrom our data(see the last entries yb2o3 1.9(6) 2.5(10) 2.3(6) 3.8(8) 3.4(4) 3.4(8) in Table l),where Me indicatesY plusthe other metals lzo3 3s.6(20) 33.3(35) 31.5(21) 35.2(35) 34.4(14) 33.7(2€) rho2 0,2(21 0.4(41 0.3(4) substitutingfor it, remainsclose to the theoreticalvalue cso 1.0(9) 1.8(2) 2.8(13) 1.r(5) 3.1(9) 4.0(9) of 1.0,showing lack of extensivesubstituuon of B or Be Fs 11.9(17) 10.2(3) 8.r(23) 1r.5(14) 8.2(20) S.S(12) a similar conclusionis reachedby consider- 25.8(6) 25.8(5) for silicon; sio2 24.8(8) 25.1(10) 25,4(41 24,r15) bonddistances (see below) or B2O3 2.3 4,2 4.0 ing the valuesof the Si-O (BS) 8.6 7.5 1.9 the mean-squarcarnplitudes obtained from crystal- (szo) 0.8 1.1 L.2 structurerefinement. Our resultsseem to contradictthe rolrls 96.4 96.6 96.9 aboutgadolinite from other 0.99 assertionsof someauthors tr€lsi* 0.98 0.95 o.g7 t.ooS o.9s (1964),Chdst (1965)]' RaE/y" o.22 0.25 0.30 0.31 0.2r o.2r sourceslsee forinstance: Oftedal calyE o,o5 0.09 0.16 0.06 0.16 O.21 but are in agreementwith the findings of Miyawaki ar al. (1984);moreover, in our case,because of the low (!0) (11) (12) aaatle (?) (8) (9) of origin, thepossibility of suchsubstitution La2o3 0.5(2) O.2l2l temperature &2o3 1.6(2) - o.s(s) 1.3(4) - ol2(1) in the Alpine environment(especially for the fissure Pr2o3 0.3(1) 0.412) specimens)is low. Full occupancyof the tetrahedral Nd2o3 r..6(3) - 1.0(5) 3.6(9) 0.2(3) 0.6(2) positionby Si may be a generalrule for all specimensof s62o3 0.9(3) - 1.1(5) 3.8(17) 0.3(4) 0.6(2) cd2o3 2'4141 O.?(3) 2,9172) 3,9l2At r.5(14) 1.9(3, gadolinite. Dyzo: 3.1(1) 1.6(0) 4.6(3) 5.4(21 3.2(9) 4.8(6) The valuesfor beryllium andwater reported in Table Er2o3 1.6(4) 1.4(4) 2.8(13) 2.6(9) 2.5(6) 3.4(5) I havebeen deduced from crystal-chemicalconsidera- Yb2o3 r.29t 1.5(4) 2.s(8) 2.0(9) X.7(10) 2.4(3) (plus boron), a l:1 atomicratio with 31.1(25) tions. For BeO yzo3 34.6(16) 41.s(17) 31.1(19) 21.5(67) 28.0(49) there is no ?ho2 0.3(3) resoect to Si has been assumed,because !o2 0.3(2) evidencefor appreciablesubstitution of Si by lighter cao 0.8(2) 1.7(4) 0.4(15) 3.2(24) ?.9(28) 3.7(8) elements. F€o 10.5(8) lx.0(10) x1.?(26) 4.0(14) 5.9(13) 9.3(13) was found in some - Whereasthe presenceof Fe3+ Mno O.4l2l gadolinite slo2 23.5(2s) 2s.8(10) 23.4125t 23.41151 29.51211.2s.01211 natural and syntheticmembers of the series BzO: 0.9 x.4 0.9 3.2 Nakai 1938,lto l967,Ito & Hafner 1974),here the (Beo) 8.1 8.9 4.2 - 7.r averageFe-O distancesin all the sampleswe have (szo) 0.3 0.6 0.x 2.o by X-raydiffraction rangefrom2.ll 4to2.199 m!6! 92.! 96.6 9!.7 89.6 examined u6/si- 1.oo o.ga 0.94 0.98 0.99 0.98 A (seebelow). These values are in the usualrange for RsE/y"" 0.24 0.oB 0.30 0.?3 0.2r o.27 Fe2*,and this is confirmed by the absenceof evident ca/YE o.o4 o.o7 0.02 0.27 0.50 0.21 oxidation in the samples.For thesereasons, we have considerediron to be exclusivelyin the +2 state. (wtq, mge wtdtlt x 10 foUowbg ach flgure, wttlin On thesegrounds, and considering also the depletion fleeure ud pamntJrese). Smplee: (1) Bdctstet!' Raurls, frcn iron with respect to the theoretical end-member s€ KontruB (1965)' Melner of (2) Mms, Rauds, from flsaure: (see gadolinitefrom the Alps hasbeen assumed (19?6), Ftscbetr (19??), stru8er (19?8' 1989), schebssta (19&4) below), general formula: Y.+rCa2fe;, md l{lntlsr (198?) ; (3) Belm, ossol,a' frcm flssuF: se calmcbl to obey the chemical (19?9)i (4) Hopffeldbodo, obemulzbachtal, lnm flesure: so Be2-282.Si2O1oHz,*zn+,, or (l-y)Y 2Q'2yCaO'(1-l) strusr (1981), sohsb€sta (1982) and PFite (1988); (5) Furta F eo.2SiOz.(2-22)BeO'zBzOr'("r+fz)H2O.Here' the pa- (lpfer (1979); (6) val tum61, Val BedEtto, fmm flssure: oa rametersr, , ande havebeen determined for eachsample Nalps, cmublinden, fmm flssre: s@ Puker qL3!: (1940) i (7) contentsin iron, calcium, andboron, nstndan, peg@dte: by measuringthe Anogno, Val Vlgezzo, frcm 8s llaxtiou our determinatioaof (19??, (8)'Bo6@n, vlgazzo' frcm I respectively,Unfortunately, since 19?8)i Anogno, val lngmtlte refine- s@ litatdoU (19?8) ud Alb€ttlnt (1988) . Thts to@ttty ls B€ntlotrsd the boron contentis basedon crystal-structure s nANogton lB our worA on Alplne xsaotlme (Demrdn 6t al. ment, our generalchemical formula can be used only 1991b)i (9) Monte Bssstta, Val Vtgozrc, fmm pagmdts: 8@ where the necessaryX-ray-diffraction data are avail- TuroDl (1982) i (10) Glogstafelb€lg' Val Fomza, fmm flsaure, able;for this reason,the entriesrelative to BrO3,BeO' ln us@l8don wtth mnadte-(Nd) (Grcer & sahmder 198?); HrO, and the total, are left blank for five samplesin (11) Trtolet, Mont Bl,anc, fmmftssm (PalsMom 1990) i (12) A\E Table1. veglta, slmplol, lmm flss@: rc AlbErdnl (1980). $ This ftgre general ratios MelSi t (atonlc) Whereasin the stoichiometric ls not rallable, o*ing to ovesdmdon of Y. Ratlo of with respectto the psldou tt (atonlc) of tbe to are satisfactory,the totals are low the metals ln ttre Y to sl. nado !!! I can Y. g Rado (atomlc) of Ca to Y. theoreticalvalues. In any case,the totals in Table

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be raisedif minor amountsof the lessabundant i?EE EAA&E 3. I'INT-CEL! DAIA OI AI.III'E CADOI,II'IIIE, AITD (which aresurely present, although below the detection couPanl60t rITB oltEB AOOnCES

limit) areconsidered. Another reason for thelow values r (A) b (A) c (A) 8(') of the totals can be incipient metamictization(see BSckstein, Rau!t6(t) 4.711(31 7.s31(8' 9.92O17) 90.53( s) below). X@s, Raurl€ (2) 4.747(Il ?.s44(1) 9.931(1, 90.5r. ( 1.) Beure,OaBola(3) 4.143 l2l 7.568(3) 9.900(3) 90,41(4) A general gopf averageof the REE distributionfor all our f,eftuen(4, 4.754141 r.510(9) 9.s55(9) 90. ?9(? ) Alpine samplesis reportedin the frst columnin Table Val tralps(6) 4. ?45( 1) 7.56211' 9.903(2) 90.48( I ) "Strada,, V.Vlg€zzo (? ) 4.7s9 ( 1) 7.564(1) 9.96S(2) e0.43( 1) 2, together with separateaverages for fissure and 'Bosco!,V. Vig62zo ( 8, 4.743(t ) 7.51S(1) 9.933(2) 90. s2 ( l.) pegmatitesamples (columns 2 and3), theconesponding uont€ Baa64ta(9) 4.75?( 1) ?.5s3(2) 9.970(1) 90.50( 1) valuesfor selectedother (non-Alpine) samples, and the slogstaf,elb€lg ( 1O) 4.752lXl 1.62912t 9.894{2) 90.2412) overall crustal A1IE VaglLa(12, 4.139 l4t 7.s98(11) 9.926(10) 90.6S( 7) average. oadollnita- (Y) TheREE disribution clearlyreflects the Oddo-Hark- Japan(13) 4.768( 1) 7,E65121 1.0.OOO(2) 90.31( 2 I ins rule (Oddo1914, Harkins 1917), with rheelemenm cadoLintt€- (t) of odd atomic noeay(1{) 4. a0 7,60 10.07 90.a number less abundantthan the corre- oadollnlte- (c6) spondingelements of even atomic number. In the Skl€n,noeay (15, 4.42 12l 7.5Al2l 10.01(3) 90,s(3) sampleswe haveexamined so far, with two exceptions Hlnggantte- (Yb) only, dysprosium Kola(16) 4.740 12l 7.50?(3) 9.888(5) 90.4E 14) is the mosr abundantREE. in the trIngganlt* (Y) samplefrom Bosco,the contentof Yb2O3(in weight) hva(17) 4.90 7.80 10.20 equalsthat ofDy2O3,and in anothercase (Glogstafel- Hinggantta- (Ca) berg),gadolinium prevails. Japan ( 16) 4.792(4J 7.7O5111 9.996(10) 90.05(4) With respectto otheroccur- F6llit6 (Table ( rences 3), the geate$t majority of the Alpine troeay 19 ) 4.7761Lt 7.62r(21 9.756(21 e0.61(2 ) samplesshow a markeddepletion of thelighterREE (La Urneral A (20) to Nd) YCahBSt2oA (oA)2 4.66 7.48 9.a6 48.5 in favorof theother members of theseries. There Datofite

is only a minor differencebetween the specimensfrom f,aBsachuaetls (21, 4.432Q) 7.604(4) 9.636(S) 90.4011 | fissuresand those from pegmatites:the heaviest REE are Eerd€rite-(Otr) slightly more Blaztl (2?' 4.S04(1) 7.661(r.) s.a1912) 90.02( l) abundantin the former, and ytrium is Uina6g€lalslte more abundantin the latter.A moresisnificant differ- arazll (23) 4.102lrt 7.562ltl 9.833(2) 90.46{ 6) encebetween the two kindsof occurrenieis thecontenr of boron,which is lowerfor thepegmatite specimens. Saqlrlss fen 1 to 12 are labelsd @ in Tabls 1. (13) Mtyamfd st a1. On the whole,t}re average distribution of REE(plus (1984), 12.08 wt6 FeO, no BzO3. (1.4)NtlBs€D (19?3) . (15) Seg8lstad & IaBs (1978), about 10 wtA FeO, 0.55 wtg 8203. (16) Voloshtn et al. ytrium) is not far from the generalaverage given by (1983), 1.31 wtg FeO, uo 8203. (1?) geBerov et al. (1,963),niDeEl not Aleksandrovaet al. (1966)forone type ofoccurrence in )msd at ttrat tlBs;3,44w|%B2Ay 1.26 wtg FeO. (18) Mtyar€td et al. granitic pegmatites(compare (X987), 5.65 fiq FeO, tncs of 8203. (19) lrllyawald er at. (1985), column I with column 7 X?.03wt$ f'eo. (20) S@enov et al. (1963), g.g0 rrg FsO. (21) Fott el in Table 2); with respectto the naturalgeochemical al. (19?3). (22)Lagere Cibb8 (19?4). (23) F@!dstql. (1980). abundance,this correspondsto a markedenrichment in themiddle-heavy REE (Dy, Er).The distributio n of REE in nonmetamictgadolinite from Hundholmen,Norway, reportedby Nilssen(1973),looks even more similar ro TAILI 2. A COIIPARISON Or lt'ttE Rrf, DISTRIBUTXON theaverage of ourdata (column 5); rhereis, on theother IN A'IPINI CAIOITXNIFE, COI.iPAAED TO EEAT IN EAIOLINITE FROM OTttER L@ATJITIES hand,a remarkabledifference with respectto the other non-metamictgadolinite from Japanstudied by Miy-

(r) a2t (3) (4) (r) (6) (7) (8) (9) (10) awakiet al. (seecolumn 4), whichis considerablyricher in the lighter REE and poorerin yttrium. In our Alpine L62O3 0.1 o.4 0. 1 0.4 1.a 14.? samples,the greatestamount of lighter rare-earthshas G2O3 1.O O.4 I.1 s.2 0.5 1.6 3.1 2.4 7.2 30.4 Pr2oJ O.1 2.5 0.1 0.9 2.6 3.6 beenobserved in thefissure sample from Glogstafelberg Nd2o3 1.9 1.3 1.9 9.3 0.8 7.9 {.5 1.7 7.4 t4.1 (5.5wtVo),andthe next highestamount (4.2 wt%o),inthe sd2o3 X.9 1.3 X.s 5.4 1.1 6.0 3.6 8.1 ?.3 3.2 pegmatitesample from "Strada",Arvogno. These fig- od203 4.1 3,9 4.3 6.0 4.1 6.2 4.a 12.6 A.0 3.0 Dy2o3 4.2 9.5 6.6 8.3 1.1 9.9 7.9 11.5 6.0 3.4 urescorrespond to 11.8 wt%o a\d 8.9wt7o, respectively, E!2o3 6.2 6.9 4.r 3.X ?.A 5.4 5.3 s.6 3.0 2.O of thetotal of theREE oxides (plus Y). The Glogstafel- Yb2O3 5.1 5.a 3.a 1.2 6.8 4.6 2.A 4.3 3.3 2.0 bergsample also shows remarkably high amounts of Sm Y2O3 70.2 7O.9 76.! 58.3 65.1 59.6 66. X 45.O -50.0 20.0 t/Dy9 a.6 ?. s 11.5 7.O 4,5 6.1 8,6 4.O 6.3 5.9 andGd (8. I and12.6 w t%o of thetotal of theREE oxides), pointingout the unusualcharacter of this occurrence; Th€ va1u6, in wtt, aF @tculatsal on the lotal of the REE oxldss - note that the REE distributionof hingganite-(Y)from Y2o3. (1) Total avengs of mr data; (2) avemgs ofiii aata for Tuva(Semenov et al. 1963)is similar(compare columns flsgure q-plesr wlth ex@pdon of the epeclnen frcm glogstafelberg, aveEgs of ou! pegmtite 8 and9 in Table2). -(,3) dsta fo! saeplesi (4) freBh ssqple frcm l4lJEzu@-kyo, Jape (trfilEwall et at. 1984)t (5) fsh *ite fm, Therange gudhole€n, ofthe observedvalues for theY2O3 content Nomy (Nllssm 19?3) t (0-?) avemgw fo! gadoltdt€ frcm gmnlte peg@dtff (21.5 to 41.5 wt%o)and the atomicREEX ratio vary (Alekmdrcys at al. 1966) ; (8) clogstaf€lberg, our (9) hrrggaplte-(y), alai8i Tuva (Semenov €t al. 1983)i (10) crutal widely (Table 1). The Y2O3/Dy2O3ratio (in rermsof ev6ng€ (Taylof & McLa@ 19BS). $ sdo (by wetgbt) y2o3/Dy2q. weight),reported in thelast line ofTable 2, in generalis

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EAEIE it. DEIIAILB OF A-RAi DHrA-co:;l,Eellol AND RIFINEUEN! higher than for the crustal average.This parameleris ot gllRocllrBB otr !!P!NE OAIOLIIfIIIE important becausethe ionic radii of Y3* and Dy3* are (8) (9) (10) virtually the same;accordingly, there is evidencefor slple (2, (3) (6) (7)

processesof fractionation depending not only upon t pale€ter h differencesin ionic radius (see also Mannucci et a/. th6 6cdl 1.o 1.0 1.0 1.1 1.1 3145 1986,Demartin et al. l99la). This is in line with our N€agulsd r€fl.ns 3304 3102 3102 3079 3110 3140

observationsfor xenotime,in particularconcerning the Rtnt 0.016 0.013 0.013 0.013 0.013 0.022 0.o19 samplefrom Bosco(Demartin et al. l99lb)i it is worth IndelEnd€n! tefl.na noting that for the samelocality, the Y2O3lDy2O3ratio rtth r>3a(11 1314 r!79 7237 11a5 1204 1049 !225

in gadolinite is 25.9. Another peculiarity of the rlaal R S o.014 0.019 0.019 0.016 0.017 0.016 0.021 gadolinite Bosco is the virtual absenceof all the from aj.nal t{d' 0.032 o.032 0.034 0.o22 0.02a 0.020 0.030 REE lighter than Gd. D value ln ths Among the elementssubsdruting for Y andthe REE, rerqnttng scn@"s o.oso 0.o40 o'o4o o.o3o 0.040 o.025 0.040 generallypresent in quantities the most importantis Ca rcl& r.1r8 1.254 1.38? 1.0a? 0.9a2 0.990 1.157 of the orderof l-2uttVo CaO.There are also specimens containing up to 4 wtVo CaO (Val Nalps, Glogstafel- llha *!dth f,or aach leflectlon (degr6€6) !s equal to tro.3stano' berg); a still higher figure (nearly 8 wt%o)has been ""an j 2 /2. obtainedfor gadolinitefrom Triolet, but the analytical s n-rrr lr"l -tle"l I /rlFol t,' a.-1x1 rol-rlrci t 1*lrol2 )r -l 2/ 1/2. dataare not asreliable, owing to the extremelysmall size e cor1n1 | ro l I r" I ) (Nolu..u"tro.r-Nu.115se6 ) I presence 2, 2 of ourcrystal and to thepossible of impurities. tnet ghtt ng 6ch@s, Fl/ (rlpo) ) o(ro)-tl ( r ) + ( 9rl2 tt I / 2No\P- Unfortunately,the poor quality of the specimenpre- cludedan investigationby X-ray diffraction. due to incipient metamictization.The reduction of Small quantities of the actinides also are present' analyticaltotals may be dueto densityvariations: in fact, Thorium couldbe detectedin four cases(about 0'3 wtTo thesephenomena already appear at the beginningofthe ThO); in one caseonly (Monte Bassetta),a similar metamictizationprocess. In this respect, a classical amountof UO2also has been detected. From thesedata, example is provided by zircon (Holland & Goufried no substantialdifference between the specimensfrom 1955);another good example is shownby the minerals fissuresand pegmatites can be observed. of the ekanitegroup (Diella & Mannucci 1986' and In nearly all our specimens,the Fe content shows referencestherein); for gadolinite,the unit-cell volume substantialdeparture with respectto the idealformula of decreasesby about3%oafter heating (Ueda 1957). Some gadolinite(see below, Table 5). In one case,at least samples(no. 7) showingincipient metamictization do (Glogstafelberg),the occupancyof the Fe positionis not seemto contain appreciableamounts of U and Th. lessthan 507o;therefore, the materialshould decidedly However. suchan occurrenceseems to be well known be more properly ascribedto hingganite-(Y1,whose in this mineral(Ewing 1975). presencein the Alps hasnot beendocumented so far. It is interestingto note that this mineral is associatedwith ANALYS$ monazite-(Nd),another very rareREE mineral.For this CnYsral-SrnucruRE reason,t}le very peculiar occulrence of Alpine REE minerals, first mentioned by Graeser & Schwander Whereverpossible, transparent fragments of single (19S?),appears to be evenmore unusual. The depletion crystals of gadolinite were mounted on a NONIUS of Fe is in agreementwith the resultsof refinementof CAD-4 diflractometer, using MoKcr radiation (1, the site occupancy(see below, Table 5); this rulesout 0 .7 1073 A; . tntensity datafor the structurerefinements thepossibility for calciumto bepresent in theFe site,as were obtained from seven specimens;in addition to in minasgeraisite(Foord et dL l 986),since otherwise the these,for threesamples, only unit-cell data could be inferred occupancywould be greater than the corre- obtained,from a least-squaresfit of25 reflectionswith spondingvalue determined by microprobeanalysis. 20 rangingfrom 30oto 38o;these are compared in Table AlthoughX-ray dataof good quality canbe obtained 3 with thoseof relatedminerals. The minor variations from singlecrystalsofmany of ourAlpinesamples,even areundoubtedly due to compositionaldifferences. withoutheating, signs of incipientmetamictization seem For the boron-richsamples, the valueof c tendsto be to be indicatedby the width of the X-ray-diffraction small;this is consistentwith thedifferences in unit-cell peaks of some samples,even if these are perfectly parametersbetween gadolinite and either datolite or transparentand show sharp crystal faces. This spreadhas homilite. The value of c seemsto be particularly been accountedfor by selectingan appropriatescan- sensitivealso with respectto the i?EE distribution.For width in ourcollection of X-raydata (see the second line instance,for the specimenfrom Japan(which is richer in Table4). in lighter REE elementsthan our Alpine samples),the Sincethe lowesttotals for the compositionsreported valueof c is large;following this trend,it is still larger in Table 1 correspondto the highestdegrees of peak for gadolinite-(Ce)from Norway(Segalstad & Larsen broadening,these effects may, at leastin part, both be l97a). In any case,the volume of the unit cell of

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SABLE 5. cot{paalsolf BsrrEEr INlERetO!{tC DrgTAltcEa ({l Ilr !,t.plnE oAlrolxttME

aaap1€ (2, (3) (6) (7) (8' (9) (10, Y{(1) 2.306121 2.29912\ 2.3O5(21 2.322(21 2.3!0(21 2.37612) 2.313(2) Y-O(l)' 2.373121 2.29912t 2.30612, 2.324(2' 2.3rO(2, 2.3nQ I 2.316(2) r-o(2) 2.172(21 2.376121 2.37L121 2.3aO(21 2.369(2t 2.3a0l2, 2.372(21 v-o(3) 2.6AL(21 2.677(21 2.677121 2.69712' 2.677121 2.695(2\ 2.661121 ' Y-o(3) 2.459121 2.474(21 2.47412' 2.467 l2l 2.4s2121 2.457 l2l 2.5O212't r-o(4, 2.36412' 2.365(2' 2.369(21 2.37AQl 2.36412't 2.374121 2.368t2t Y-o(s, 2.490121 2.s1412' 2.506(21 2.491121 2.4A7(2t 2.50rl2l 2.52O121 y-o(5), 2,4O6(2t 2.423121 2.416121 2.39A(2t 2.38A(2t 2.394(2t 2.446(2, Y4(av€rage) 2.424 2.424 2.42A 2.432 2.420 2.429 2.A3A t occupancy 1.1.7 1.07 1.09 1.19 1.09 1".77 1.36 B.V. €@ 2.AO 2.14 2.17 2.73 2.83 2.76 2.69

3r-o(1) 1.604(2) 1.607(2) 1.603(21 r.672(21 7.607(21 r.613(2) 1.611(2) si-o(2, 1.636(2) 1.63s(2) r.63e(2) 1.635(2) 1.634(2, 1.638(2) 1.628(2) st-o(3) 1.633(2) r.635(2) 1.634(2' L.63rl2t L.62712l r.632(2) 7.633121- s1-o(4) 1.64212' L.645(2t r.64012) 1.645(2) 1.641(2) 1.650(2) 1.634(2) Si-O(aY6!a9€) L.629 1.63X 1.631 1.631 I.627 1.633 7.627

Be-o(2) 1.629(3) 1.606(4, r.6U(3) 1.540(3) 1.633(3) 1.638(3) 1.601.(5) 86-0(31 1.64r(3) 1.619(4) 1.62s(3) 1.64?(3, 1.647(31 1.646(4) 1.63r(51 B€{(4} X.614(4) r..597(4) 1.598(3, 1.628(3) 1.628(3) 1.630(41 1.598(s) Bs{(s) 1.604(3) 1.se8(4) 1.s9s(2) 1.605(3) 1.589(3) 1.602(3t r.622t5t Bd(averag€l 7.621 r.607 I.6]2 1.638 1.636 1.638 1.610 B occutscy 0.16 o.29 0.26 0.08 0.10 0.08 0.24 B.V. a@ 2.06 2.75 2.!4 2.02 2.05 2.03 2.77 Forul chuge& 2.f6 2.29 2.26 2.OA 2,r0 2.OA 2.24

Fe-O(21x2 2.2ef(2, 2.275121 2.27912t 2.29r(21 2.27312) 2.2A6(2t 2.29a(21 F6{(4)x2 2.223(21 2.221,121 2.22512t 2.227 12) 2.22O121 2.222(2, 2.24A(21 re-o(s)x2 2.O3sl2l 2.O45121 2.O44121 2.03512t 2.O2Al2t 2.O37(21 2.0s212' F6-O(aver. I 2.190 2.140 2.1a3 2.144 2.L74 2.182 2.199 !e occupancya 0.66 0.50 0.54 0.76 0.a2 0.78 0.22 Ps occupscy- O.70 0.54 0. s9 0.s6 0.80 0.92 0.30 B.V. s@ 1.96 t.94 1.94 1.94 1.99 1.95 1.A7

B.v. sa [o(5)l 1.48 1.34 1.39 1.51 1.58 1.58 1.2X.

The atom are l8boled ac@rding to lliyawau el al. (1984) i. tlF nmberilg of ths samplsa ls ths @o s l|r Table 1. " FrcE crlBtal-structure analysls;" D frcE results of electmn-nlcrcprcbe enalyass. Bond-valence au h v.u. (Brcm 1981). . Se ten.

gadolinitedecreases with increasingcontent of the replacementof Y by the heavierREE, the occupancy heavierREE elements,as expectedfrom the lanthanide for yttrium is always greater than unity, even where contraction.As for hingganite,if theposition of the Fe appreciable quantities of calcium also are present atom is not fully occupied,the unit-cell parameter, (Table5). tendsto be larger,in line with the increaseof the Fe-O The refinementwas carried out separatelyfor each distances(see below, and Table 5). crystal by full-marix least squares,minimizing the For the crystalsof best quality (irregular fragments quantity Zw(Fo-F")z, and considering a total of 82 whosediameters range from 0.1 to 0.2 mm, untreatedby variables.These include symmetry-unconstrained posi heating or other manipulations),reflections with a tional and anisotropicthermal parametersfor all the maximumvalue of theBragg angle 0 of 35. with MoKa atoms, plus the scale factor, an overall extinction radiationhave been collected. Detailed data about such parameterand the occupancyfor Y and Fe. The atomic collections are reported in Table 4. For all crystals, coordinatesof the startingmodel were those of Miyawa- empiricalabsorption corrections were derived according ki (1984). 'psi-scan" etal. Theweighting in thelast cycles, the final to the techniqueof North et al. (19681, valuesof the R index and the correspondingweighted followed by the DIFABS routine (Walker & Stuan index rR* are reported in Table 4. Fractional atomic 1983),as describedby Demartinet al. (1992). After coordinates,anisotropic thermal parameters and tables correcting for absorption, the disagreementfactors of structure factors are depositedat CISTI, National betweenthe Fo valuescorresponding to symmetrically ResearchCouncil of Canada,Ottawa. Ontario KIA 0S2. equivalent reflections in the same crystal are quite All the calculationswere performedon a PDPlll73 satisfactory(Table 4). computerusing the SDP-PlusStructure Determination Scattering factors for neutral atoms, along with Package (Frenz et al. 1980). In the final Fourier correctionsfor anomalousdispersion, have beentaken differencesyntheses, no peaksexceeding 1.1 - 0.6 e/A3 from Cromer & Waber (1974) and,Cromer (1974), have been found. Thesepeaks are always close to the respectively, including the real and the imaginary REE position and do not imply presenceof additional part.For &e REE,we haveassumed the scatteringfactor atoms. of Y. Because of this assumption,and the partial Interatomicdistances are reported in Table5, together

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with values of the e.s.d. The main features of the tion betweenthe Be-O and the Si-O averagebond- structureare in closeagreement with the conclusionsof lengthshas been observed. the earlier works on tle samesubject, especially with In the Japanesematerial studied by Miyawaki et al. thoseof Miyawakiet al. (1984),which is takenhere as (1984),the average length of theBe-O bondis 1.634(2) the main reference.The minor differences we have A. This valueis significantlylargerthan the correspond- observedare significant but caneasily be explained.For ing resultsfor all our Alpine specimens;similarly, there instance,the average(Y+i?EE")-O distance in our sam- are significant differenceseven within our set of sam- plesis 2.428A, a smallervalue than the conesponding ples, in contrastwith the uniform valuesfor the Si-o average(2.437 A) found by Miyawaki et al. Tttis is bondlengths (see Table 5). Themost plausible explana- clearly relatedto the differencein the proportionof the tion for all this involves partial replacementof Be by REE,our samples being poorerin the lighterREE, whose otherelements.Of thesesubstituents, Si canberuledout, ionic radius is comparativelylarge. This result of the sincethe Be-O and the Si-O bondsare very similar in lanthanidecontraction is evidenteven within our set of length. Instead,boron is the most likely candidate,in samples,the smallest(Y+REE")-O distance (2.420 L) view of the structuralrelationships between gadolinite and the largestone (2.438A) being observedfor the and datolite.For the latter mineral,the averageof B-O samplesfrom Bosco and from Glogstafelberg,respec- distancesis 1.480(l)A @antA Cruickshank1967, Foit tively (Table 5). Among the specimensfor which data et al. 1973),avalue much shorter than the averagevalue arereported in this table,the former is the poorestin the (1.65A) reportedbyOndik & Smith(1962) fortheBe-O lighter lanthanides,and the latter is the richest.In some bond length; for lromilite, the correspondingaverage cases,these average distances and especiallyt}te occu- distanceis 1.504A (Miyawakiet al.1985). pancy of Y also are affected by the presenceof Since in datolite and in many members of the significantamounts of Ca; the smallestfigures for the Y gadolinite seriesone atom [correspondingto O(5)] is occupancycorrespond in fact to the specimensthat are totally or partially replacedby an OH group, the relatively rich in Ca and Y and poor in the lanthanides. shrinkingeffect due to thesubstitution ofBe by B could In general,the Fe-O distancesof our samplesare very becomeless clear, because the bondswith OH would closeto the valuesobtained by Miyawaki et al. (1984)a differ in length from the correspondingbonds with the averagesfor ou1specimens can be comparedwith oxygen.For this reason,a betterresult can be achieved the average(2. I 82 A) obtainedby theseauthors. For the if the Be-O(5) bond is not considered,and the average Glogstafelbergsample, these distances are slightly but of the remainingthree Be-O bond lengths is usedfor significantly larger than for all the others.This differ- comparison.This- averageamounts to 1.475 A for enceis probablydue to the absenceof a largepart of the datolite.to 1.530A for homilite,and to 1.648A for the iron atoms,whose presence would counteractthe elec- Japanesegadolinite, respectively (Foit et al. 1973, trostatic repulsion betweenthe neighboring atoms of Miyawaki et al. 1984, 1985), the last value being oxygen. practically identical to the generalaverage of Ondik & The averageSi-O distancesfor each one of our Smith (1962).In line with theseresults, the Be-O(5) crystals (see Table 5) do not show remarkable distancefor theGlogstafelberg sample [1.622(5) A] is differencesfrom the general averageof al1 our data remarkablydifferent from the correspondtngdistances (1.629A); the correspondingvalues inMiyawak:, et al. for all theother samples, including Nos. 2, 3 and6, which (1984,1985) for gadoliniteand homilite (1.633 and also are B-rich (1.595to 1.604.A, respectively).This 1.634 A, respectively) are only slightly larger, and confirms the possibility of the presenceof a significant the difference may not be significant. With respect amount of OH replacing O, thereby supporting our to the range of averagelength of the Si-O bond^in assumptionof a relatively high water content:a similar well-documented orthosilicates (1.628-1.655 A), conclusioncan be drawnon thebasis of a bond-valence as for instance in the olivine-monticellite group summation(see below). (Brown 1970) or the garnetgroup (Novak & Gibbs By carrying out a linear interpolationwith respectto 1971),our valuesare situatedat the shorterextreme, theseend membersof known composition,the occu- but there is substantial agreement, taking the pancyfactor for B (in the Be position)reported in Table possible overall influence of the crystal structureinto 5 has been calculatedfor all our specimensfor which account. adequatecrystal-structure data are available. This index Our datathus confirm the virtual absenceofreplace- correspondsto a B2O3content ofthe orderof l-3 wtVo, mentofSi by otherelements, especially boron. Further- with a maximumof 4.2 wtVofor the samplefrom Beura. more,since in the caseofthe presenceof any substituent Thesefigures are not surprising; accordingto Oftedal in two different structural sites a partition coefficient (1964),the B2O3content of 81 samplesof gadolinite betweenthese sites is implied,the highestamounts of from 22 differentlocalities ranges from 0.05to 2.5wtEo, boron substituting for Be should correspondto the with an averageof 0.2wtVo.Inmost cases, B2O3 ranges highestconcentrations in the Si site; if theseconcentra- between0.05 and O.5wt%o; another study by Aleksan- tions are significant, a considerableshrinking of the drovaetal. (1966)showed appreciable amounts ofB2O, Si-O bond-lengthshould result. However,no correla- (up to nearly 5.0 vtt%o)in gadolinite samplesfrom the

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USSR.Therefore, our resultsfor the Alpine specimens list ofreferences.The authors are also grateful to Dr. G. are in the range of values already reported in the Robinsonfrom the CanadianMuseum of Natureas well literaturefor gadolinite. asto R.F. Martin for invaluablehelp and advice. On applyingbond-valencesums (Brown 1980),there is a general,although only qualitative,agreement with REFERENcES the observedsubstitutions, as can be expectodfor partly disorderedstructures. For instance,for the Be site, this ALBERTM,C. (1986):Gadolinite dell'AlpeVeglia (Ossola-No- sum rangesfrom 2.02 to 2.15,and the highestvalues vara).Riy. Mineral. hal. 9, 179-181. correspondto the highestcontents ofboron (seeTable 5); however,if the bond-valences is assumedto be a - (1988): La pegmatitedel Bosco, Arvogno (Valle weighted averagefor Be and B (s = 2 and 3, respec- Vigezzo,Novara) . Riv.Mineral. Ital. ll,65-72. tively), the valuesare slightly different (seethe next line in Table 5). A similar situationoccurs for Fe. wherethe AI-EKSANDRovA,I.T., Gnznunc, A.I., KwnryanovA. I.I. & lowestvalence-sum (1.87) is obtainedfor the sample SIDoRENKo,G.A. (1966):Geologiya Mestorozdeniya EIe- from Glogstafelberg,which is the poorestin Fe. For lnentov: Redkozemel'nyeSlfftary. Vses. Nauchn. Issled. InstinrteMineral'n 26, Nauka" Moscow. O(5),whose bond-valence sums are reported in the lasr line of Table5, thelowest value ( l.2l is alsorelarive ro ) BnowN, G.E. (1970): The Crystal Chemistry the samplefrom Glogstafelberg, of the Olivines. which, accordingto our Ph.D.thesis, Virginia Polytechnic Institute and State Univ., chemicalconsiderations, should be the richestin water Blacksburg,Virginia. (OH).However, t}re corresponding values for O(5)in the othersamples never exceed 1.58, even for theOH-poor BRowN,I.D. (1981):The bond-valencemethod: an empirical specimens.For theY site,the bond-valence sums range approachto chemicalstructure and bonding./r, Structure from2.69to2.83;here, the correlation with thechemical andBonding in CrystalsII @4.O'Keeffe & A. Nawotsky, compositionis lessclear. eds.).Academic Press, New York (1-30). The partialreplacement of Be or Si by otherelements could also be reflected in the refined values of the CelaNcHr,N. (1979):Brevi segnalazioni:gadolinite di Beura occupancyfactor; however, attempts in this respecthave (Val d'Ossola).Riv. Mineral. Ital. 1,49-50. failedto givereliable results. Similarly, ifthe occupancy (1965): is not refined, the average (apparent) mean-square Crnrsr, C.L. Substitutionof boronin silicatecrystals. NorskGeol. Tidsskr.45" 423428. displacementshould show appreciablevariation with respectto the 0normalOvalue. However, the thermal CoLBy, (1968): parameters J.N. Quanriftive miooprobeanalysis of thin are difficult to compareand interpret,since insulatingfilms. Adv. X-ray Anal.11,287-305. they vary considerablyfrom one sample to another, showingthe combined effectsof differencein number Cnoturn,D.T. (1974): Intemational Tablesfor X-Ray Crystal- ofelectrons,ofvariation in bondlengths, and ofresidual lography4, Table2.3.1. The Kynochhess, Birmingham, absorption. U.K. (presentdistributor: Kluwer Academic Publishers, Thebond angles around Si rangefrom about106o to Dordrecht Holland). 117o,and tlose aroundBe, from l01o to 116., in agreementwith the tendencyof oxygen-bondedberyl- - & Wasrn, J.T. (1974):Intemational Tables for X-Ray lium to form lessregular tetrahedra than either silicon or Cry s tal l og r aphy 4, T able2.2.b. T\e Kl,nochPress, Birmin- boron. gham,U.K. (presentdistributor: Kluwer AcademicPublish- ers,Dordrecht, Holland).

ACKNoWLEDGEMENTS DEMARTTN,F., Gnavaccror-r,C.M. & Pu-en,T. (1992):The importanceof accuratecrystal-structwe determination of This work has been made possibleby financial uraniumminerals. II. Soddyite(UO2)2(SiO4)(2HrO. Acta assistancefrom the Italian NationalResearch Council Crystallogr.C48,I-4. (C.N.R.).We are grateful to a numberof collectors,most of whombelongtothe Gruppo Mineralogico Lombardo, -, Prant, T., Drplm, V., Dor.rzsllr,S., GENrr-E,P. & who provided us with most of the necessarymaterial, Gneuacctot-t,C.M. (1991b):The chemical composition of often sacrificing unique specimens.These are: Messrs. xenotimefrom fissuresand pegmatitesin the Alps. Can. ClaudioAlbertini, DomenicoPreite, and Franco Vanini. Mineral.29.69-75. Special thanks are due to Mr. Ronald Winkler from Bbcksteinand & Gnarr,raccroLlC.M. to Dr. GerhardNiedermayr for theAusfian (1991a): specimens, Alpine monazite:further data,Can. Mineral. 29, andto Mr. Alex Kipfer for the samplesfrom 6t-67. Switzerland.We arealso indebted to Dr. AndreaValdrd from the Analytical Departmentof Philips (Milan) for DELLA,V. & MANNUccr,G. (1986):A uranium-richekanite, havingperformed qualitative the analysesforboron. Dr. (Ths.76,Ue.21)(Ca2.61,Fee.ea,Mnn.6 1)Si7.eO26, from Pitiglia- Michael Fleischerkindly suppliedus with a very useful no, Ialy. Rend.Soc. Ital. Mineral.Petrogr.4l,3-6.

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VotosHrN,A.V., PergouovsKlr,YA.A., MEN'sHlKov,yu.p., Received October 27, 1991, revised manuscript arcepted PoVARENNyK,A.S., Marvnenro, E.N. & Ynrunovrcn. April22,1992.

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