1295

TheCanadian Mineralogist vol. 37,pp.1295-l3OI (1999)

ONEILLITE:A NEWGa-DEFICIENT AND FEE-RICHMEMBER OF THEEUDIALYTE GROUPFROM MONT SAINT.HILAIRE. QUEBEC. CANADA

OLE JOHNSENS

GeologicalMuseum, University of Copenhagen,@ster Voldgade 5-7, DK-L350 Copenhagen, Denmnrk

JOEL D. GRICE ANDROBERT A. GAULT

ResearchDivision, Canadian Museum of Nature,P.O. Box 3443,Station D, Ottawa,Ontario KIP 6P4, Canada

AesrRAcr

Oneillite, ideally Na15Ca3MnjFe3 Zr3Nb (Si25O73)(O,OH,H2O)3(OH,C1)2, is a new member of the group from Mont Saint-Hilaire, Quebec. It occurs as yellowish brown anhedral grains up to 2 mm in diameter. Associated include , , and . It is transparent to translucent, with a vitreous luster and white . It is brittle, with a hardnessof 5-6 (Mohs scale).It has no ,no parting, and an uneven . It is uniaxial negative with o 1.6450(3) and e |.6406(3).It is trigo^nal,space group R3, a 14.192(l) and c 29.983(3) A, V SZf Olt.t 43, Z = Z. The strongest X-ray powder- diffraction lines [d in A (D@kl)] arc: 11.348(44.2)(101),7.100(33X110), 6.021(36.1X021), 5.683(30 8)(202), 4.291(36.5X205), 3389(42 9)(141), 3.199(30.8X208),3.150(34.9)(23'1),2.964(100)(345)and 2.844(89.1)(404).The infrared spectrumis given. An electron-microprobe analysis of the grain of oneillite chosenfor refinement of the structure gave NUO 13.6O,KzO 0.28, CaO 2.9O,MnO 7.70, FeO 3.00,SrO 0.09,A12O3 0.18, Y2O3 0.78, La2O3 2.88, Ce2O3 5 14,Pr2O3 0.48, Nd2O3 1.45, Gd2O3 0.20, SiO2 43.46,210211 44,HfO20.16, M2O5 3 48, Ta2O50.14, Cl 0.76,H2O 0.63,O = Cl0.17, total 98.58wt.%. The proportionof H2O was calcuiated from stoichiometry on the basis of the crystal-structure analysis. The empirical formula of oneillite, based on 78.09 anions as determined in the crystal-structureanalysis is: (Nar+:uR.EErs:&zoSroo:)>tan (CatnREEossNag66)>302 (Mn276Y62a)1360(Fera:MnoqoZrozs)>zsq (Zr2e3Nb665Hf{ro:)>:or (Nbos5Taooz)>orr (Siz+rrAlorz)>z+ss OI:(O,OH,HzO):oq (OHr zuClor:)>zo0.D^.u.= 3 20{3).D.u1" = 3.22\31glcmj Comparedto the eudialytestructure, the uniquefeature in oneillite is the ordering of Mn and Ca + REE atthe Ml site, which lowers the symmetry from R3m to R3. Determination of the was dependent on the recognition of a merohedral twin. The REE content is the highest hitherto reported, with REE occupying almost 50% of Na(4).

Keywords: oneillite, eudialyte, new species,crystal structure, merohedral twin, Mont Saint- Hilaire, Quebec, Canada.

Sotvnaarnr

L'oneillite, dont la composition iddale est Na15Ca3Mn3Fe3 Zr3Nb (Si25O73)(O,OH,H2O)3(OH,Cl)2, est une nouvelle espdce mindrale, membre du groupe de l'eudialyte, provenant du mont Saint-Hilaire, Qu6bec. On la trouve en cristaux brun jaundtre atteignant un diamdtre de 2 mm Lui sont associ6salbite, sodalite, pyrite et aegyrine. Elle est transparented translucide, avec un dclat vitreux et une rayure blanche. Elle est cassante,et sa duret6 est 5-6 (6che11ede Mohs). Elle est sans clivage, sansplan de sdparation,et se casseavec une ftacture in6gale.!'oneillite est uniaxe n6gative, avec o 1.6450(3)et e 1.6406(3).EIle est trigonale, groupe spatial R3, a I4.192(l) et c 29.983(3) A, y 5230(1) tt3, Z = 3. Les raies les plus intenses du spectre de diffraction X, mdthode des poudres [d en A (I)(hkl)l sont: 11 348(44.2)(101),7 100(33)(110),6.021(36.1)(021),5.683(30.8)(202), 4 29r(36 5X205), 3.389(42.9)(141),3.199(30.8)(208), 3.150(34.9X23'7),2.964(100)(345) et2.844(89.1)(404). Nous pr6sentons le spectred'absorption dans I'infra-rouge. Une analyse i la microsonde 6lectronique du cristal choisi pour l'6bauche de Ia struc- ture cristallinea donn6(en Vo,poids) Na2O 13.60,K2O 0 28, CaO 2.90,MnO 7.70,FeO 3.00, Sro 0 09, A12O30.18, Y2O30.78, La2O32.88, Ce2O35.14, Pr2O30 48, NdzO: 1.45,cd2o3 0.20, SiOz43.46, 2rO211.44, HfO2 0.16, Nb2Os3.48, Ta2O50 14, Cl 0;76, H2O 0 63, O = Cl 0.17, pour un total de 98.58. La proporlion de HzO a 6t6 calcul6e d partir de la stoechiomdtrie, telle que confirm6e par I'analyse de la structure cristalline La formule empirique de l'oneillite, sur une base de 78 09 anions aussi d6termin6epar 1'analysede la structure,est: (Nar+:zZR153Ks2651663)tr16 13(Cal 77ZRs5eNao66);362(Mn276Y62a)13es (Fer +:Mno qeZro25);2 6a (Zr2 e3Nbe65Hf6 s3)23 61 (Nbs 35Ta062)16 s7 (Si2a77Als 12);z+rq O7:(O,OH,H2O)3 ee(OH1urClo r:)>u oo D^* =3.20(3), Dc* = 3.22(3t g/cm3.Par rapport d la structure de I'eudialyte, l'aspect distinctif de I'oneillite est la mise en ordre de Mn et de Ca + ZR (terresrares) sur le siteMl. C'est ce qui abaissela sym6trie de R3mdR3.L'6barche de la structurecristalline

F E-mail address: oj@savik geomus.ku.dk t296 THE CANADIAN MINERALOGIST n'a 6td r6ussie que par prise en compte d'une macle m6ro6drique. La tensur en temesrares est la plus 6lev6e qui soit connue; en fait, les terres rares occupent presque 507o du site Na(4).

Mots-c16s:oneillite, eudialyte, nouvelle espdcemin6rale, structure cristalline, macle m6ro6drique, Mont Saint-Hilaire, Qu6bec, Canada.

IxrnooucrroN The holotype specimen was collected in the Poudrette quarry at the contact between a vein of fine- During a systematic study of the chemistry of the grained albite and the host rock, nepheline syenite. As- Na-rich zirconosilicate eudialyte (Johnsen & Gault sociated species are albite and sodalite, with minor 1997), severalprivate collectors contributed specimens pyrite and aegirine. Only one specimen was collected that enabledus to samplea broad spectrumof eudialyte- containing approximately 100 mg of oneillite; to date group minerals from various occurences. One ofthese no fuilher sirnilar material has been found. specimens,sent to us by Colonel (Ret.) Quintin Wight of Ottawa, Ontario, was shown to be a unique, Ca-defi- Pnvsrcar- ANDOprrcAL Pnopnnrres cient, rare-earth-element-richmember of the . This sample, which is the holotype specimen of Oneillite occurs as yellowish brown, anhedralgrains the new speciesdescribed here, oneillite, was collected up to 2 mm in diameter in a fine-grained albite matrix. from the PoudretteQuarry,, Mont Saint-Hilaire, Quebec It is vitreous, transparent to translucent, with a white in 1994. The purpose of this paper is to describe this streak. It is nonfluorescent in short- and long-wave ul- new member of the eudialyte group, its structure and traviolet light. It is brittle, with no cleavage,no parting occuffence. and an uneven fracture. It has a Mohs hardnessof 5-6. Oneillite is named in honor of John JohnstonO'Neill The of oneillite, measuredby suspensionin me- (1886-1966),a geologistwith the GeologicalSurvey of thylene iodide, is 3.20(3) g/cmj, which compares well Canada and later a professor of geology at McGill Uni- with the calculated density, 3.22 glcm3. versity, Montreal, Quebec. He was the first to describe Oneillite is uniaxial negative, o = 1.6450(3) and e = the geology of Mont Saint-Hilaire and the first to report 1.6406(3) (\ = 589 nm); some grains show an anoma- eudialyte and other rare, peralkaline minerals at this lo- lous 2Vup to 15 + 2" (sample 9 in Johnsenet al. 19911. cality (O'Neill 1914). A graduareof McGill, Yale and The mineral shows no pleochroism. A Gladstone-Dale the University of Wisconsin, Dr. O'Neill was a member calculation gives a compatibility index of -0.004, which of the famous StefanssonArctic Expedition of 1913- is rated as superior (Mandarino 1981). 1918 and later went on to become Dean of Science and Dean of Engineering at McGill University. CnBlrarcar-Corr.rposrrroN The new mineral species and its name have been approved by the Commission on New Minerals and Chemical analyseswere done in wavelength-disper- Mineral Names, IMA. The holotype specimen of sion (WD) mode on a JEOL 733 electron microprobe oneillite (catalogueno. CMNMC 81565) is housedin using Tracor Northern 5500 and 5600 automation.Data the collection of the Canadian Museum of Nature in reduction was done with a PAP routine in XMAQNT Ottawa. (pers. commun., C. Davidson, CSIRO). The operating voltage was 15 kV, and the beam current was 20 nA. OccunnsNcs Data for all elements in the sampleswere collected for 25 s or 0.507o precision, whichever was attained first. Mont Saint-Hilaire is an alkaline intrusive comolex Forty-six elementswere sought,but only those detected and one of the ten Monteregian Hills. a seriesof geneti- are reported here. The presenceof H2O in oneillite was cally related plutons aligned along the St. Lawrence confirmed by infrared spectroscopy and crystal-struc- Valley for almost 150 km eastward from Oka to ture analysis.Standards used in the electron-microprobe Megantic in the province of Quebec.It hasbecome well- analyseswere: vlasovite (NaKcr, SiKa,ZrLa), sanidine known for its diversity of mineral species (Horv6th & (KKa), diopside (CaKct), celestine (Srlcr), tephroite Gault 1990); indeed, this diversity is also exhibited in (MnKa), almandine (FeKct), chrysoberyl (AlKcr), a set the wide variation in chemistry in the eudialyte-group of synthetic REE phosphates (Lalcr, CeLa, PILB, minerals from this locality (Johnsen& Gault 1997).In Ndlct, GdZa), synthetic garnet (YIG) addition to oneillite, two other membersof the eudialyte (YLct), synthetic hafnon (Hffa), synthetic MnNb2O6 group, and ,have Nbfct), synthetic NiTa2O6 (TaLa), and marialite recently been described from Mont Saint-Hilaire (ClKa). Data for the standardswere collected for 50 s (Johnsenet al.1999). or 0.25% precision, whichever was attained first. For ONEILLITE, MONT SAINT.HILAIRE, QUEBEC 1297 oneillite, two analyseswere performed on two separate IwrnenpoANaLvsIs grains taken from the unique specimen. The composi- tion of the grain selected for structure analysis is re- The infrared spectrum of oneillite (Fig. 1) was ob- ported here along with the range of the results: Na2O tained using a Bomem Michelson MB-120 Fourier 13.60(13.60-13.62), K2O 0.28 (0.23-0.28),CaO 2.90 transform infrared (IR) spectrometer with a diamond (2.90-313), MnO 7.70 (6.98-:7.70),FeO 3.00 (3.00- anvil cell as a microsampling device. The broad absorp- 3.01),SrO 0.09 (0.00-0.09),Al2q 0.18 (0.11-018), tion bands at3309 and 164'l cm-r are assignedto the YzO: 0.78 (0.744.'78),LuOz 2.88 (2.87-2.88),Ce2O3 [OH] stretching mode and the [H2O] bending mode, 5.14 (5.11-5.14),Pr2O30.48 (0.42-0.48),Nd2O3 1.45 respectively.The two small bandsat 1455 and 74'14cm-l (1.38-1.45),GdzO: 0.20 (0.00-0.20),SiO2 43.46 are attributed to the stretching mode of a [CO3] group. (43.4644.35), ZrOz 1r.44 (1r.44-rr.48), HfO2 0.16 Although the amount of (CO:) is small, it is sufficient (0.00-0.16),MzOs 3.48(2.91-3.48), Ta2O5 0.14 (0.0G- to register on the IR spectrum, which is extremely sen- 0.14),Cl0.76 (0.76-0.82),}]2O0.63, O = Cl0.l7, total sitive to the presenceof any molecular vibration modes 98.58 wt.Vo.The proportion of H2O was calculated by of a crystal. These two bands are also noted in stoichiometry from the crystal-stl'uctureanalysis. The manganokhomyakovite (Johnsen et al. 1999) and empirical formula of oneillite, basedon 78.09 anions,as (Johnsen et al. 1998). The (CO3) group determined in the crystal-structure analysis, is (Na1a37 can be accommodatedwithin the crystal structure at the REEI 53KszoSro o:)>,re r: (Car rREEo ssNaooo):: oz Fl site.Note that the disorderedFl site has bond lengths (Mnz reYo z+)>3(Fe1 a3Mns e aZro zs)>za+ (Zr2 e3Nbes5 F1a - F1b of 1.26(2) A in a trigonal array (bond angle Hfo o:):: or (Nbo ssTa602)>0 ar (Siz+rrAlo n)>z+ aso73 11'7.9[6]'), much like that of a (CO3) group. The bands (O,OH,H2O);3os(OHr ztClon)>zor, ideally, Na15Ca3 at92'7,9'r.8,and 1013cm-r areassigned to the symmet- Mn3Fe3Zr3Nb(Si2sO73XO,OH,H2O)3(OH)2. ric stretching of [SiOa] and indicate considerable split-

(! E Ess

2500 2000

wavenumber (cm-1)

Frc. 1. Infrared spectrum of oneillite 1298 THE CANADIAN MINERATOGIST ting of the [SiOa] vibration modes, attributable to a mode on a flat sample.Intensities were measuredwith a structure with crystallographically distinct [SiOa] linear position-sensitive detector with an aperture cov- groups.Bands at 662,684,706 and 741 cm-r are as- ering a range of 6" in 20, a step scan of 0.01', and a 20 signed to bending of [SiOa]. Bands at 406,455 and 485 range 5-90o; the total time of data collection was 65 h. cm-1 could not be unequivocally assigned,but are likely Least-squaresrefinements basedon 8l reflections gave due to vibrations involving the larger polyhedra, with the unit-cell parameters:a 14.192(l), c 29.983(3) 4,. bond distances greaterthan 2 A. The crystal-structure analysis of oneillite was done on two different crystals with concordant results. The X-Ray Cnysreuocnepny single crystal of oneillite used for the collection of X- eNo Cnysrer-Srnucrunp DernuaIxeloN ray-diffraction intensity data presentedin this paper is a ground sphere0.12 mm in diameter. Intensity data were X-ray powder-diffraction data collected on a Stoe collected on a fully automated Siemens four-circie transmission-typediffractometer are shown in Table 1. diffractometer operated at 50 kV and 40 mA with graph- CuKctl radiation was selected,with a curved Ge mono- ite-monochromatized MoKs radiation. A set of 50 re- chromator, and data were collected in transmissionscan flections was used to center the crystal and refine the

TABLE I. ONEILLITE: X.RAY POWDER_DIFFRACTIONDATA

r/k d*. 4rJA) hkl ah 4.r"(A) hkt

44.2 I1.348 I t.372 I u I 7 4 2.253 2.253 5 8 199 9.997 9 994 0 0 3 2.251 l0 289 9.480 9.505 0 I 2 4.2 2.216 2.218 6 I 33.0 7.100 7.096 I /0 8 8 2.184 2 t84 6 2 169 6387 6 399 I 0 8 9 2.167 2 t66 6 5 36 1 6.021 6.020 0 2 t5 2 2.146 2 t46 0 t0 5 6 5.789 5.786 I 2 r 1.9 2.130 2 132 5 7 308 5683 5 686 2 0 2 129 4 l1 6 0 5.377 5 389 0 I s 9 2.048 2 048 0 0 7.0 4.998 4.997 0 0 6.1 2042 2 043 t2 4291 4 292 2 0 36 5 2 042 6 2t9 4086 4 086 I 2 6 69 2016 z 016 7 282 3948 3.948 2 J 8.6 2-006 2.006 6 5 8 3.67Q 3.672 I 3 5 l l 8 1.97s | 974 o 581 3.585 0 I 8 8.0 3 6 E r.932 1.931 7 185 3549 3.548 2 2 0 40 1909 1910 2t4 3512 3.514 0 2 76 1901 | 902 6 8 42.9 3.389 3.387 I r 901 0 5 l0 IJ.J J.JZ+ 3.324 3 96 1.895 0 o 6 30.8 3.199 3.200 2 0 65 1.792 0 2 l6 34.9 3150 3 149 2 3 10.6 1 757 0 4 t4 4 | 3-107 3.103 I 60 1.745 0 6 I 4.8 3.058 3.057 0 1,744 5 8 2 299 3 013 3.016 I z 9 5 E 1.710 3 8 4 n t.709 3010 0 2 82 1.696 i 695 2 0 17 1000 2.964 2.963 3 ) 8.4 1.694 1.694 5 7 t4 3 2.892 2 893 2 6 | 693 2 8 2 89.1 2.844 2 843 4 0 4 6.6 1641 | 642 1 4 lo 5.5 2.808 2 807 3 I 5.6 1622 | 622 I 2 l8 1.4 2.770 2.771 2 2 7 9 1.600 1.600 A 0 l6 102 2694 2 695 0 10 8.7 1.590 1.590 5 8 8 12.4 2 667 2 667 I 7 1.589 1 7 l0 2.641 2.639 10.6 3 40 1.574 1 <11 4 6 t4 29.4 2 5E5 2.585 0 a 57 I )OZ 1.561 3 5 t6 128 2521 2 522 3 8 't.546 58 I 545 5 7 l2 2.519 2 l0 54 r.536 1.537 1 6 t4 44 2498 2.498 0 tz 1.494 1.494 2 3 l9 2.497 7 1 494 7 9 z 110 2375 2.376 0 8 't.477 133 2366 2.365 3 0 7E t.477 5 9 7 q, I I 0 2.317 2.3t6 2 I r.431 r 430 0 6 l5 4 5 2.267 I l3 )-z t.427 1427 I 3 20 62 1.408 l 408 l0 I

Stoe diffractometer data, trmsmission mode on flat smple; CuKol radiation Indexing basedon c eII: a = 14.192(I), c = 29.983(3) A, y = 5230(l) A' . ONEILLITE, MONT SAINT-HILAIRE, QUEBEC 1299

TABLE 2. ONEILLITE:CRYSTAL DATA AND STRUCTUREREFINEMENT

Sample identification oneillite (sample 5 in Johnsen& Grice [1999]) Wavelength 0.710'13A Crystalsystem; space group Trigonal;-R3 Unit-celldimensions, 4-circle data a = 14'2084(81A' c = 29.959(3)A Volume 5237.8(7)A' Crystalsize spherediameter 0.12 mm 0 range for data collection 2 04 to 30.06' Index ranges o < h s 17,0 s k s 17,-42 < I < 42 Reflections collected 3815 Refinement method Full-matrixleast-squares on ,d Data / restraints / parameters 3803/01426 Goodness-of-fit on -d 1.043 = = Final R indices [>2o(1)] Rl 0.032,wR2 0.072 R indices (all data) Rl = 0.036,wR2=O.074 Isotropic refinement R! I wR2:0.070 / 0.I 33 Largest diff. peak and hole 1.01and -0.84 e'A-3 \.r merge before/after 1.16I 0 87 lR-rl 0.'702 effectof TWIN command Rl: 0.107-+ 0.032

cell parameters. Assuming a non-centrosymmetric 1990) packageof computer programs. The final refine- rhombohedral cell, one asymmetric unit of intensity data ments were done with the SHELXL-93 program was collected(i.e., + h + k+ I) up to 20 = 60o using a (Sheldrick 1993).The strategyapplied to the final stages 0:20 scan-mode,with scanspeeds inversely proportional of the refinement as well as the site-assignmentproce- to intensity, varying from 3 to 29.3"/minrte. The data dure were describedin detail by Johnsen& Grice (1999). collection consistedof 3815 reflections with more than The final atomic coordinates,isotropic displacement 857oobserved (i.e., F" > 4o F").Information relevant parameters and selected bond-lengths for the oneillite to the data collection and structure determination is structure are presentedby Johnsen & Grice (1999, given in Table 2. sample 5). Lists of observed and calculated structure- For the ellipsoidal absorption correction, 15 intense factors and of anisotropic displacement factors have diffraction-maxima in the ftnge 12 to 60" 20 were cho- been submitted to the Depository of Unpublished Data, sen for V diffraction-vector scans after the method of CISTI, National ResearchCouncil of Canada, Ottawa, North e/ al. (1968). The converging R for the V-scan Ontario KIA 0S2, Canada. datasetdecreased from l.l6Vo before the absorption correction to 0.8'lVo afterthe absorption correction. The DsscmpuoN ANDDlscussloN oF THESrnuctuns excellent convergenceattests to the near-sphericalshape of the crystal. The minimum and maximum transmis- Oneillite is a member of the eudialyte group' As sion factors for the linear-absorption corrections are described by Johnsen & Grice (1999), the structure of 0.604and 0.585, respectively. Assigning phases to a set eudialyte-group minerals consistsof layers of six-mem- of normalized structure-factorsgave a mean value I E4- bered rings of [M(l)Oo] octahedra (mainly Ca) joined | | of 0.702, strongly indicative of a non-cenffosymmet- by IM(Z)O"I polyhedra (Fe or Mn) and sandwichedbe- ric space-group. The I Et - 1 | value is significantly tween two pseudo-centrosymmetricallyrelated layers of lower than for other samplesof eudialyte, which have three-membered and nine-membered silicate rings form- values in the range of 0.79-1.04 (Johnsen& Grice ing a2:l composite layer. The 2: I composite layers are 1999). The incongruously low value of I E2 - 1 I for crosslinked by Zr in octahedral coordination and are oneillite is a result of merohedral twinning (Herbst- related to one another in accordancewith the rhombo- Irmer & Sheldrick 1998). The structure was solved and hedral symmetry. Voids in the open structure are filled refined in spacegroup R3. The structurerefined to R1 = with five distinct [Na@n] polyhedra, of which the 0.107 both in R3m and R3 until it was recognized that [Na(4)O,] polyhedron is particularly suitable as a host the ru-plane in ordinary eudialyte is a twin plane in of relatively healy elements such as REE and Sr. M(3) oneillite. After the introduction of the twin operator,the and Si(7) are two central sitesof the two crystallographi- R1 index dropped to 0.032. Reduction of the intensity cally distinct nine-membered silicate rings, and related data, structure determination and initial refinement of by ihe substitutiont6lM(3) + t4ls(7) <+ 2t4lsi(7).in the structure were done with the SHELXTL (Sheldrick which M(3) typically is occupied by M. 1300 THE CANADIAN MINERALOGIST

Ftc. 2. A six-fold ring of altemating tM(Ia)Oel and [M(1b)O6] octahedra with auached [SiOa] tetrahedrain oneillite viewed along [001].

The principal property that distinguishes oneillite rzedby an exceptionally low content of Ca, only 1.77 from other members of the eudialyte group is the cation apfu, and contentsof Mn and Nb that are among the high- ordering of M(1) into two distinct sitesM(la) andM(lbS est reported. The concept of a solid-solution series be- altemating in the six-fold ring, which destroys the mir- tween the classiceudialyte, rich in Si, Ca, Fe and Cl, and ror planes (Fig. 2). Ca is normally the primary element kentbrooksite(Johnsen et al. 1998),rich in Nb, REE,Mn in M(l) with Mn, REE and Y as the corlmon substitu- and F, as presented by Johnsen & Gault (1997), was ents. As the ratio Cal(Ca + Mn + REE + Y) in M(1) modified by Johnsen& Grice (1999), who proposedthat decreases,the [M(1)O6] octahedron, with an average the series extends beyond kentbrooksite to the eudialyte- bond-length equal to 2.35(2) A, becomesmore distorted group mineral now described as oneillite. until it splits into a relatively small and a relatively large octahedron.The smaller [M(la)O6] octahedron,with an AcrNowr-socBNaeNts averagebond-length of 2.227 A, accommodatesmostly Mn, whereasthe larger [M(1b)O6] octahedron,with an We are grateful to Quintin Wight who provided us averagebondJengthof 2.431A, accommodatesCa and with the specimen used in this study. Peter Tarassoff the REE (Johnsen& Grice 1999). kindly provided information on the career of J.J. In oneillite, REE ue also accommodatedin two of O'Neill. The authors acknowledge financial support the Na sites, primarily in Na(4), where REE constiture from the Danish Natural ScienceResearch Council (OJ) close to 507oof the population. In total, the REE content and the Canadian Museum of Nature (JDG and RAG). (10.15wt%o REE2O3, -2.12 atomsper formula urut (apfu) Helpful commentsfrom the referees,T. Bikett and P.C. REE,Y2O3 not included) is the highest content hitherto Burns, and the editor R.F. Martin improved the quality repofted in the literature. Oneillite is further character- of the manuscript. ONEILLITE, MONT SAINT-HILAIRE, QUEBEC 1301

Repr,nnNcBs eucolite - mesodialyte - eudialyte terminology. Neues Jahrb. Mineral, Monatsh., 37 I-383. HBnssr-IRMen,R & Snplonlcr, G M (1998): Refinement of twinned structures with SHELXL9T. Acta Cmstallopr. M,q.roenno J A. (1981): The Gladstone-Dale relationship. IV. 854,443-449. The compatibility concept and its application. Can. Min- eral. 19,441-450. HoRvArH, L. & G.lulr, R.A. (1990): The mineralogy of Mont (1968): Saint-Hilaire, Quebec. Mineral. Rec. 21, 284-360. Nonrn, A.T.C., PutLlns, D.C. & MlrHBws, F.S. A semi-empirical method of absorption cofiection. Acta JonNsBN,O. & Geulr, R.A. (1997): Chemical variation in Crystallo gr. 424, 351-359 eudialyte.Neues Jahrb. Mineral., Abh. l7I,215-237. O'NErLL, J.J. (1914): St. Hilaire (Beloeil) and Rougemont GnrcB,J.D. & Encrr,T.S. (1999): Mountains, Quebec. Geol. Surv. Can., Mem.43. Khomyakovite and manganokhomyakovite, two new mem- bers of the eudialyte group from Mont Saint-Hilaire, Susl-ontcr, G.M. (1990): SHELXTL, a Crystallographic Com- Quebec, Canada. Can Mineral. 37, 893-899. puting Package (revision 4.1). Siemens Analytical X-ray Insffuments Inc., Madison, Wisconsin & GnrcE, J.D (1999): The crystal chemistry of the eudialyte grotp. Can. Mineral.37, 865-891. (1993): SHELXL-93. Program for the ReJinement of Crystal Struclures. University of Gdttingen, Gtittingen, & Geulr, R.A. (1998): Kentbrooksite Germany. from the Kangerdlugssuaqintrusion, East Greenland,a new Mn-REE-Nb-F end-member in a serres within the eudialyte group: description and crystal strucfi)re.Eur. J. Mineral. 10,20'7-219.

_, PsrEnsEN,O.V. & GAr,'r-r,R.A. (1997): Optical data Received May 12, 1999, revised manuscript acceptedAugust on minerals of the eudialyte group: discussion of the 29, 1999.