t45 TheC anadian M brc rala gis t Vol.35, pp. 145-r5r (1997)

ADDITIONALSTUDIES ON MIXEDURANYL OXIDE-HYDROXIDE HYDRATE ALTERATIONPRODUCTS OF URANINITEFROM THE PALERMOAND RUGGLESGRANITIC PEGMATITES. GRAFTON COUNTV, NEW HAMPSHIRE

EUGENEE. FOORD1

IJ.S. Geolagical Survey, Denver Fedzral Center,.Box 25M6, Mail Stop 905, Dewer, Colarado 80225, U.S-L

STANLEYL. KORZEB 13993East Arkona Avmuz, Aurora, CoLorado80012, U.S.A.

FREDERICKE. LICHTE U.S.GeoLogical Suney, DenverFederal Cewer,Box 25M6, Mail Snp 973, Denver, Colorado80225, U.SA.

JOANJ. FIT?ATRICK U.S.Geolagical Survey, Dmver Fedcral Cewen Box 25M6, Mail Stop912, Denver, Colorado80225, U.SA-

ABSTRACT

Additional studieson an incompletely characterizedsecondary 'hineral" from the Rugglesand Palermogranitic Fgmatites, New HampshAe,refened to as "A' by Frondel (1956), reveal a mixnre of schoepit€-goupminerals and related nranyl oxide-hydroxide hydrated compounds.A compositechemical analysis yielded (in wt-Vo):PbO 4,85 (EMP), UOa 83.5 (EMP), BaO 0.675 (av. of EMP and ICP), CaO 0.167 (av. of EMP and ICP), KzO 2.455 (av. of EMP and ICP), SrO 021 (ICP), ThO20.85 (CP), HzO 6.9, D9.61. Powder-diffractionX-ray studiesindicaJe a closeresemblance in paffemsbetween mineral "A" atrd severaluranyl oxide-hydroxidehydrated , including the schoepitefamily of mineralsand UOz(OFI)2. The powderdiffraction data for mineral "A" are most similar to those for syntheticUOzrlSHzO and UOz(OII), but other phasesare likely presentas well, TGA analysisof both mineral 'A' and metaschoepiteshow similar weigbt-loss and first derivativecurves. The dominantlosses are at 100'C, with secondaryevents aJ 4{Do and 6@"C. IR spectrashow the prasenceof (OII) andHzO. from both pegmatites,analyzed by LAM-ICP-MS, showsthe trresenceof Tlt Pb, K and Ca"

Keywords: mineral 'A', uraninite,schoepite, UO2(O[I)2, Rugglas pepatite, Palermopegoarib, New Hampshire.

Somaens

Des dtudesadditionnelles portant sur un nindral secondaired'rnanium despegnatites granitiques de Rugglaset de Palermq au New Hampshire,dont la caractdrisationdemerne incomplBte [c'est le mineral "A" de Frondel (1956)], monnent qu'il s'agit d'un m6langede min6raux du groupe de la schoepitee1 de compos6soxydes-hydroxydcs hydrat6s d'uranyle. Une analyse chimique compos€ea doon6,en pords,PbO 4.85 (microsonde6lectroniEre, MSE), Uq $.5 (MSE), BaO 0.675 (moyennede MSE et plasmaI couplageinduct'f, PCD, CaO 0.167 (moyennede MSE et PCD, KzO 2.455 (moyennede MSE et PCD, SrO 0.21 (PCD, ThO2 0.85 (PCD, H2O 6.9, >99.61. ks €tudespar difhaction X (m6thode des poudres)r6vdlent une grande ressemblanceentre les spectresdu min6ral 'A" et plusieursoxyde+-hydroxydes hydraf6s d'uranyle, y inclus les min6rauxdu group de la schoepiteet UO2(OI{)2.D'aprds les donn6esde diEfractionX le min€ral "A" ressembledavatrtage aux compos6s synthdtiquesUOz.ee.1.5HzO et UQ(OII)2, nais il est probable que d'autes phasessont aussi impliqu6es. Une analyse thermogravim€triquedu min6ral "A" et tle la m6tashoepitemontrent un taux de perte de poids et une courbedu premier d6riv6 assezsemblables. Les pertesimportantes sont d 100'C, avecdes 6v6nements seconrlaires i 4@oet i 600oC.Le spectreinfra-rouge r6vblela pr6sencede (OII) et de HzO. Des&hantillons d'uraniniteprovenant des deux pegmatiGs, analys6s par PCI avecablation au laser et spectometriede masse,contiennent Tb" Pb, K et Ca (fraduit par la Rddaction)

Mots-clds: min6ral "A', uraninite,schoepit€, UO2(OII)2, pegnatite de Ruggles,pgmatite de Palermo,New Hampshire.

I E-mail addr"ss: [email protected] 146

INIR,oDUc"iloN other analytical methods,including gas chromato- graphy,X-ray diffraction Q(RD), and transmissionin- An unknownand incompletsly chracterized 3'mhetral" frared spectrophotomety,were utilized during the study o, of wanium was originally describedas phase'A" by of mineral "A uraniniteand schoepite,and tle resul- Frondel (1956) as part of a study on "gummite". Addi- tant data were used to determinethe na.tureof mineral tionalsflrdies wereconductedonmineral "A" in anafiempt "A". IJnsuccassfrrlattempts were made to determine to fully characterizeit asa new species.Uraninite, from unit-cell dimensions from powder-diffraction data four localities, also was chemically studie{ and their using the zone-axismethod of Visser (1969), and to ages determined. Metaschoepitefrom Shinkolobwe, interpret these data by Rietveld structure analysisby Zaire, was chemicallyanalyzed and studiedby thermo- B.C. Chakoumakosatthe OakRidgeNational Laboratory, gravimefiic analysis(TGA). Oak Ridge, Tennessee. Samplesof phase"A" from two bodies of granitic ooA" pegmatite,the PalermoNo. I and Ruggles,were used Tlfi NeruRE oF UNK].IOWN in this investigation.The PalermoNo. 1 pegmatiteis locdted near North Groton Village, Groton, Grafton Mineral "A" is oneof a numberof mineralsid€Nrtind County, New llampshire, andthe Rugglespegmatite is in "gummite" (Frondel 1956).This mineral was found located in Grafton, Grafton County, New Hampshire at six localities, all in granitic pegmatites,at North lseeFig. 1 of Korzeb et al. (1997)1. Wilton, Pale, o, Ruggles,Alst€aq andBeryl Mountairl New Hampshireand at GrassyCreek, Mitchell County, METHoDSor Irrwrsrrcanot North Carolina. We believed it to be a new mineral speciesbased on the X-raypatiems obtained.However, Specimensof phase '4" were obtained from the chemical and structural studreswere not completed. collection of the Harvard University Mineralogical Additional unpubiishedwork was doneon mineral o'A" Museum (HUI4I/Q collection and from Mr. Robert by Frondel (C. Frondel, pers. comnt", 1994 and C.A. Whitnore, Weare,New llampshire.Electron-microprobe, Francis, trErs. comm., 1993). We have attemptedto TGA, (LAM-ICP-MS) laser-ablation microprobe - further clarify the statusof Mineral "A" using maferial inductively coupledplasma - rnassspectometry, and from PalermoNo. 1 mine and Rugglesmine.

-.1 -!. j'i. :r::ii

-ii! : *.:,i;s;

FIc. l. Photographshowing the variable alterationof uraninite to mineral "A". Palermono. l' HtIMlVl# 13205. The width of thefield of view is 1.8cn- PRODUCTS OF ALTERATION OF IJRANINITE 147

oomineral" TADI.B1. CHBMICAL @MPGIr!ON OF MINERAL !A! Mineral "A" is the first to fotm as an FROMTHB PALBRMOMINB GROTON NEW HAMTSHIRE alterationproduct of uraninite(Figs. 1, 2). We alsohave o'mineral'o Elmdc EMP&dCC LA-ICP-MS Co[palte idenffied ttris from several pegnaiites in orldg @lF6 (wr %) a$lysb (wt. A) @lysls (wL %) Maine and Nortl Carolina" and from the Monticello Pb 4J. fluorite disni4 New Mexico. In al1cases, the "minemlo' u 69.tr is a distinctive orangeto yellow-orangecolor. K 0.s Cg 0.0v Resuls of a compositechemical analysis for mineral BA 1.7 ooA" 213 ar€given in Table 1. Additionalanalyocal daJa were s 0.721 providedby TGA for weightloss as a functionof tempera- c 0.07 N 0.01r fire, andby I,AM-ICP-MS formore tlan 70 eleme,lrts. T@l 98.3:t The analyticaldatainTable 1 indicateacomposition Uo3 E5.3 E3.$ very similar to that of two samplesof "gummite" from Tho, 0.85 0.8y Mtchell County,North Carolin4 which yielded X-ray rbo 3.0 4.85, BaO 0.01 0.67f powderpafterns for mineral "A" in Frondel'sstrdy. An ko. 0.07 Yrot o.a averageof the two compositionsafter subtractionfor Cao o.26 0.16?6 uranophaneand FezO:is: BaO 1.6 wt,Vo,PbO8.25Vo, &o 3.n 2.455! SrO 0.21 0217 UOt 8l.5Vo, H2O 8.657o, 2L00J wt.Vo, sro 6.9 6.9 Resultsof aLAM-ICP-MS analysisof mineral "A' Total 100.39 9.@l from the Palermomine are given in Table 2. All of the lead presentis radiogenic,and the 26Pbt2ntPbratio is TGA btal wdgli !c b LmC - 8.i6 wL%, subhadng 186wt% bsue of cwsdcr of UOr b U& betum 80$'md 1@^c qlra h a total of 6J9 0.053,yielding a calculatedage of.329 Mu wt%. Total @b (rufc): 69 wt%r Wts t{tft TGA dtu" 0.72 wl% H There are several significant differences between s&[.|3d b EtzOis 65 wL%, avaluet!@ble ag@twdrEte altoed (EMP) deffiutlodt duab otat Chedol arulyto w@ d@ by a nebo of the electron-microprobe results and the refirodc dsEedcroprobemlysfmU, O, Bq K Pb mdcarc dmby LAM-ICP-MS results.The LAM-ICP-MS showedno KL wsrrdr (U56, Dsru), gsr d'mabgnply aulyo fm ll c, md N, by EMP. The level of Pb dre m arylewedglis 6 1429& dtd,8^a \Wrc*pecdvely,rc dreby cJ. Ba, as opposedta L.2 wt.Vo ed OS6, Rest6r),edlhem![detmhdsr (baat +, md, (CadEalE determined by EMP is greater than that obtained tttntt@) rc dsE by LL ta*m (tls6, Dsvs} I a@ge od 3 by LAM-ICP-MS. On the other hand, K is higher by debi#raffotai, mge of 4 mlyaeE s rcge of 5 mlt8€S I rege of 6 m1,€€4 tEMP; 6rcgeof EMPdtdICFmlte; zICP. LAM-ICP-MS thanbyEMP. - :iq .i.,!?'.

i.s! n*h* i fFfu -$ i&s ffi ,;tr .#

Frc. 2. Photogra,phshowing a closerview of the variablealteration of uraninite to mineral "A' and relaled secondaryuranium minerals@alermo no. 1). HIIMM# 132005.The width of the field of view is 6 mm. 148 THE CANADIAN MINERALOGIST

TAELB 2. POWDM, DIMACTION DATA FOR MINERAL'A' FROM lgE PALERMO AND RUCGLESMINES, MAFTON COTJNTY,NS.

Mreral'A" Mhsal'A' Mlneral'A' UO2g'1.5&O p-UOr'2&O Rugglosdm Palernomlne hlermo nine ICDD 2!1,161 ICDD All40l Frodel(1950 (thlsp4er) Powderdffiastomele(

de w deI4 IA de d* I/t d& I/I" d& 4 7.U 7.38' 10 ?.E0 t9 7.4 7.n lm 7.53 6.37 7 6.35 6 49 6.n 6.n t0 6.37 5 S.m 2 5.9r . 5 5.32 E 5.09 5.10 2 5.gl x 4.gr 4.70 I 3 4.80 4.n' t 4.49 5 4.26 10 4.26 5 4.V2 I 4.m 3 3.98 3.90 l 9 3.95 3.956 15 3.7t 3.70 30 3.76 4 3.75 3.49 10 3.50 l0 l0 3.528 3.5n lm 3.56 4 3.55 10 t.49 49 3.439 X.431 4 3.4 15 3.376 3.380 50 3.32 7 3.?tt 7 3.n 8l 3.Ut 3.?39 lm 3.n | 3.21 3.lE 7b 3.20 & n 3.92 3.tCl 55 3.11 6 3.16 I 3.(D 3.V2 5 3.04 6 6 3.(b 2 2.vl 6 2.X9 2.W 5 2.% 2.90 3b 26 2.94 2.9tf ?n 2.v2 7 2.91 l0 2.863 2.K2 5 2.U | 2.n | 2.8t4 2.8@ 3 2.80 5 2.6 3 2.6E 5 2.&5 5 2.4 2.6t 3b 2.6 2 61 2.@ 2.gt 15 2.5Vt 3 2.61 15 2.551 2.550 5 2.sr3 2 2.54 31 2.45 2.45 5 2.49 2 2.4 4 2.44 4 2.t8 23m 5 2.38 2 2.N l0 2.% 3 2.33 5 2.313 2.3t3 3 2.32 2 2.30 2 2.n 5 22S 2 2.25 12 2.26 2.2M 5 2.n 2 2.t2 5 2.17 3 2.n 5 2.16 | 2.t6 5 2.t43 2.141 3 2.15 2,@ I 2.10 3 t 2.t93 2.tu t0 2.13 3 2.r3 n 2.053 2.(E3 l0 2.6 4 2.gl 11 2.O8 2.@3 5 2.U 2.6 2 2.8 2 31 r.94 t.W 30 2.m 3 2.01 t0 t.ytg t.vtg 30 Lm 3 1.963 ? 1.951 1.954 3 1.945 r.92 3b r.93 2 5 r.$5 2 1.91 1.87 I 5 1.881 1.881 10 1.88 2 t.&l l.t2t t0 l.& t.8t I 1.80 2 3 L1m L1m ll t.7E Ln6 45 r.Tt:) 10 l.Tro 1.?5 3 1.75 3 6 t.74 t.78 35 Ljn 13 t.7t7 t.7t6 l0 r.T8 PRODUCIS OF ALTERATION OF IIRANINITE 149

TABLE 2. - Continued

1.5 t.6 0.5 t.62 1.5 l.6l 4 r.593 1.593 0.5 1.585 l.57 I 0.5 1.580 L9 I 31 1.525 1.525 0.5 1.564 7 L84 1.486 12 1.438 1.438 I 1.4{n 1.4q] 7 Lno r.370 2 Lng t.3x) 7 l.wI 1.1ts 2 LrrS 1.295

Nob: Powderalaa colleoted udng a SienensD-5il1 imurc.u, 0.@' steplisemenl, z) sec@dcoltrt 'nes IE inrrcm€fi, 45 kV, 35 EA, CuKal O.54{59A)rtdladon, NBS940 dlicon usedas 8n inEmal stasalsr&DatB fton Frondd (1956)are fton Deq|e-Schsrr€(114.6 nn fflm anddaa h colum 2 8'e ftom 114.6m dlameterGandlolf, 6lnr.

A cmvergeDt,five-cycle refiremeu fu mineral'A' yioldsa sc,hoepie-tlTeorthorhoEbic cell with: a 14.Ilq3)A b16.831(4)L c14.766{)4. LinesmrkedwihanareriskwemrejecEdhthereficne4 8[ ofhgrssers sccepbd llowver, no erdrcdon codtdoDsrers usedfrr &e rc0trem€rt

A pdbte tmAreodmbas8d m avallabledat0 b that*e havsa mbdne of UQo l.5SrO, p-UOr'2grO ando&€r stuclrtsl derfradvecof fu cchoepie-gpeudt cetl, whtcl ls orppo'ledby 6s chetni$tyetttch ls 6ai ofsclo€ptb ad tts strucfiral dertradves.

The only mineralsthat areclosely relaled chemically Infrared sp€ctra(KBr peilet technique)of mineral and struchrrally to mineral "A" are membersof the "A" from 200 to 4,000 wavenumbersshow the pres- schoepitefamily: schoepite,[(uo2xor(oH) p](Elzo)p; ence of both (OID and H2O. Additional unidentified metaschoepiie,UO3.1-2H2O; dehydrated schoepite, vibrations are presentaI 2925 (tipleQ, 650, 620 and 8[(UO2Oo.25)(OII)r.s].Ia addition,at leasttwo synthetic 465 wavenumbers(Fig. 3). uranyl oxide hydrates[UO2s6.1.5H2O (formerly known A determinationof specificgravitywas madeon five as o'paraschoepite")and UO2(OH)21bear some simi- grains of mineral o'A", aggregating7.5 mE, using a larity to mineral "A". Crystal-chemicalstudies of the Bermanmicrobalance. An averageof tbree determina- various hydratesof schoepiteand other uranyl oxide- tions gave 5.45(2), A calculateddensity for schoepite hydroxidehydraies wele doneby Christ & Cla* (1960). (tuily hydratpd)using the data in Finch et al. (1996u

4([n WAVENUMBER(CM{)

Ftc. 3. Transmissioninfrarcd speclrum for mineral"A" from the Palennomine. 150 TTTECANADIAN MINERALOGIST

1997)is 4.88,which is significantlyless than the 5.45 very low lead contentis indicative of a young age for determinedfor mineral "A". the schoepite, as opposedto the primary uraninite, X-ray-diffraction studieswere donefor mineral "A" which contains9.L wt.VoPbO and has a calculatedage using I14.7-mm diameterGandolfi cameras,and CuKcl of 1,040million years. radiation.A powder patternusing NBS 640asilicon as After heating (o 1000"C), the "schoepite" (meta- 'A'both an internal standardwas made of mineral 'oA'oon a schoepite)fromT-afue and mineral give iden- SiemensD-500 diffractometer.All of the X-ray data tical X-ray-diffraction pattems. The resulting black indicatethat thereis a very closeresemblance between powder is the high-temperaturerhombohedral form the patternsfor mineral'A'and the schoepitefamily of (CDD file no. 8-2214)of U:Os. Heatingstudies at 350" minerals,as well as severalsynthetic compounds, The and 500"C indicate the existenceof additional, as yet X-ray data for syntheticUO46.I.5H2O and UOz(OII)z unidentified,phases intermediate between mineral "A' most closely match those for mineral "A" (Table 2). andU3O3. Becauseof the extemely fine grain-size, no single- crystal X-ray studiesare possible. STTIDIES oF URANIMTE A unit cell for a schoepite-typemineral or other uranyl oxide-hydroxide hydrate was soughtusing the Because a significant quantity of potassium was iterative zone-axismethod of Visser (1969), but was detectedby EMP and LAM-ICP-MS methodsin the ooA", not successfirl,even though the mineral is not metamict Rugglesmine sampleof mineral \ile decidedalso and gives sharpto relatively sharpreflections. An or- to analyzefour samplesofuraninite, all from granitic thorhombic, schoepite-typecell, using no extinction pegmatites.Sample provenance and results are given in conditions,was found (Table2). However,at leastfive Table 3. The Swamp Quarry uraninite is somewhat reflections are not indexableon the orthorhombiccell unusualin that it shows no signs of secondaryaltera- chosen.Calculated X-ray powder-diffraction data for tioo. 11s mineral is thorium-bearing(10.7 wt.VoTI::Oz) schoepite agree well with dafa reported for natural andcontains 3.19 wt.VoREEzOy schoepite/Fnch et al. 1996b).The X-ray powder pat- The lead in uraninite from the Swamp Quarry tern for the sampleof lemon-yellow "schoepite"from (2.5 wt.VoPbO), PalerrnoNo. 1 (4.6 wt.7o PbO) and Shinkolobwe,Zanre is substantiallydifferent from that Ruggles (5.9 'lut.VoPbO) pegmatitasis all radiogenic. '4", of mineral and most closely matchesthat reported TLe 207PbP06Pbratio for the SwampQuarry uraninite is for syntheticmetaschoepite (ICDD #18-1436). 0.0526,which gives an ageof 312 Ma. The ryPbAPb In addition. a Rietveld refinement of the mineral ratio for the PalermoNo.1 pegmatiteis 0.0533,which was attemptedthrough the courtesy of Dr. Brian C. gives an ageof 342Ma. For the Rugglespegmatite, the Chakoumakos,Oak Ridge National Laboratories, 20TPbPMPI.ratio is 0.0530, which gives an age of Tennessee.Unfoftunately, the high conte,lrtof hydrogen, 329 Ma. A high concentation of K was detected(by which produceda low peak-to-backgroundratio, pre- both EMP and LAM-ICP-MS) in tle uraninite from ventedacquisition of usabledata. both pegmatites(Iable 3). Likewise, Finch & Ewing To checkthe reportedwater content of schoepite,and (1992) reportenthe presenceof K from uraninite from its typ€ (i-e.,+ or -), TGA analysisof 4.8 mg of yellow Shinkolobwe.However, its role in the uraninite struc- needlesof a mineral labeled o'schoepite"(now meta- ture remainsunknown. schoepitebecause of dehydration)from Shinkolobwe showeda rapidloss of.5 wt.VoH2O by 100'C,and then a slowerloss of 6.8 vrr..VoH2O by 1000"C.The addi- tional loss occursin two steps:5 wt.VoH2O by 420"C, and the final 1.8 wt.Voby 1000'C. The loss in the secondstep is due to the conversionof UO3 to U3O8 TABLE 3. AESJLTSOF I,AM.ICP.MS A}IALYSFS OF URANIITts (1.86 wrTo O loca).The tohl weight-lms,Ll .8,nt-Vo H2O, is o)dde Susp QuEy klmotl Sbirfoldvo, also close to that (11.2 fi.7d requiredby the formula ToPshas,MB N. Gsfioo, NI{ Nottl Gstoo, NS zairc uo, 83.0 89.4 90.06' 91.3 n.5 UO3.2II2O(metaschoepite). Some H2O is readilyreleased tho, 10.7 o,n 0.43 0.35 0.m (by 100'C), but tbo (F6t) 2,5 5.9 3.63 4.6 9.1 the remaining water is more tightly !.I%o 0.m 0.50 0.27 1.0 boundin the stucture. Much, if not all, of theremaining &o 0.01 2.u 2.55 <0.01 CsO 0.10 0.t 0.81 0.18 t.6 water is likely presentas hydroxyl. lroo 0.01 0.17 0.09 0.11 o.o2 Both mineralooA" and 'schoepite' from Pelq 0.06 <0.01 0.66 0.23 0.u2 Shinkolobwe Y,O! 1.68 0.(E <0.01 0.066 showsimilar weight-loss and first derivative(rate) curves. RS2O' 1.51 0.21 zto. <0.01 0.Cr7 0.15 o.a2 The dominant losses are at 100"C, with secondary Mo,q <0.01 events at 400"C and 600'C. The chemistry of the SlO <0.01 0.08 0.01 sto" 0.2 0.47 0.80 0.46 "schoepite" was also checked by a LAM-ICP-MS ALO, 0.05 0.15 0.44 0.07 _ MgO <0.01 0.50 0.17 0,n analysis, which showed essentiallypure UO3.2H2O, Tohls 99.85 10r.04 97.@' 1m.55 99.35 with 0.25 wt.Vo PbO. Minor amounts of Na2O - 'nt.%o) NG: Shaub(193$ als ircbd6 m % Prq, &o (bbr): +1. (0.31 andK2O (0.69 vtt.Vo) were also found. The reddw0.54; "rcpodduU3Q. PRODUCTS OF ALTERAIION OF URANINIIE 151

CoNcLUsIoNs provided by J.A. McGlasson, and the sample of schoepitefromZanre was provided by J. Vajdak. K.G. In view of the current state of knowledge of the Espositoand C.G. Whitney (USGS)ran the TGA scans 'oA" pressure-temperatureconditions of crystallization in of mineral and schoepite.Reviews were provided granitic pegmatiles,it is quite reasonableto have a by P.J.Modreski (USGS),V.T. King (Rochester,New hydroxyl-bearinguranium oxide be the first mineral to YorD, RJ. Finch(Univ. ofManitoba), and W.B. Simmons, form from oxidation of primary uraninite. The calcu- Jr. and A.U. Falster (Univ. of New Orleans).We are lated agesfor the primary uraninite and surrounding grateful to all of the reviewersfor their excellentcom- mineral o'A", at the Ruggles mine are tle same mentsand suggestions.R.F. Martin provided welcome (329 Ma), and all of the lead in both mineralsis radio- additional suggestionson this and the accompanying genic. This favors a high-temperaturehydrothermal paper on the chemical evolution and paragenesisof origin for mineral "A". Completelyhydrous minerals uraniumminerals in the pegmatiteenvironmenl. (including , soddyite, uranophane-p, phosphuranylite,and meta-autunite-I,with molecular REFm.m{crs water only, surround mineral *A", and were formed subsequento it Korzeb et al. 1997).A stuctre refine- Cmlsr, C.L. & CLARK,J.R (1960):Crystal chemical studies ment of schoepitehas now beencompleted @inch er a/. of someuranyl oxide hy&ates. Am Mineral,45, n&lMI. 1996a),and the phasetransformations and crystallo- graphic relations among schoepite,metaschoepite and FlNcr,R.J., CoopB, M.A., HawTtonNE" F.C. & Ewnc, R.C. dehydratedschoepite @lorchet al. 1997) have been (1996a):The crystal structureof schoepite, clarified. [(uQ)eOr(O]D'XtlzO)'2. Can Mineral.34, 1071-1088. "Mineral A" is rare and does not occur in many R.C. (1992): The conosion of uraninite pegmatitelocalities world-wide. The/(O) seemsto be & Ewntc, nndeloxidizing conditions. J. Nucl.Maer,190, 133-156. an importantfactor in explainingits formation"because unoxidizedand unaltereduraninite is found in pegma- HavmoRNE,F.C.& Ewwo, R.C. (1996b):Calcu- tites containing columbite-tantalite-group minerals, lated X-ray powder-diffraction data for schoepite, triphyllite or magnetite [e.9., Topsham (Maine), the [(UOr8O2(O]I)rzl(HuO)tz,and comparisonwith reported SprucePine district (Nortl Carolina),Branchville and powderpattems, Powd Dif,9, (in press). Portland (Connecticut),and Moss (Norway)1. If tle /(O) is sufficientlyhigh, then any uraninitealso present & -(lW7): Phasetramfomations is partially or completelyaltered to mineralscontaining andcrystallogra;phic relations among schoepite, mehschoepite (in press). Uto. On the basisof all of the above,it seemsclear that and dehydratedschoepite. Can Mincral.35, mineral o'A'owas formed as a product of hydrothermal FRoNDE-,C. (1956): Mineral compositionof gummite.Aza crystallization alterationof uraninite very shortly after Mineral. 41,539-568. of the uraninitewithin the host pegmatites. oA" Mineral is not a single mineral,but is a mixture Konzrn, S.L.,Fooro, E.E. & Uctnq F.E. (1997):The chemical of at leasttwo differenturanyl oxide-hydroxide hydrates evolution and paragenesisof uranium minerals from the (amemberormembersof the schoepitegroup andother Rugglesand Palerrno granitic peguatites, New Hampshire. minerals currently known only as synthetic com- Can Mineral.35, 135-144. pounds)and perhapsother U-bearingminerals as well. This is indicatedby the X-ray-diffraction data,the IR ScuAItB,B.M. (1938):The occurence, and com- and TGA data,specific gravity and the chemicaldata. position of the uraninite from the Ruggles mine, near GraftonCenter, New Harysfure. Am Mineral. ?i, 33LMl.

Acro{owLEDcElmr{Ts Vrssm, J.W. (1969):A fully automaticprogram forfinding the unit cell from powder data-J, AppI. Crystallogr.2,89-95. C.A. Francis(Harvard University) andR. Whitmore 'A" providedspecimens of mineral andassociated min- Received.October 18, 1995,revised manwcript accepted eralsfor study.The sampleof uraninitefrom Zaire was OctoberS,1996.