Canadian Mineralogist Vol. 16, pp. 335-340 (1978) DONNAYITE,NaGaST'Y(CO,),.3H,O, A NEW MINERALFROM MONTST.HILAIRE, QUEBEC GEORGB Y. CHAO, PAUL R. MAINWARING aNp JUDITH BAKER Departmentol Geology,Carleton University, Ottawa, Ontario KIS 586 ABsrRAcr nite. Elle forme des groupements syntaxiques avec l'6waldite, l'6waldite strontique, la mackelveyite et, pegmatite Donnayite occurs in dykes, miarolitic mais rarement, avec la synchisite. Le facids des cavities and interstices in nepheline syenite at Monr cristaux est variable: aplati, tabulaire, prismatique, St-Hilaire, Qu6bec. Usually associated with en forme de soucoupe ou de tonnelet, en masses microcline, analcime, calcite, natrolite, chlorite, grenues. Ces cristaux, dont la taille oscille entre aegirine, arfvedsonite and other minerals, donnayite 0.05 et 2mm, sont normalement de couleur jaune commonly occurs in syntactic intergrowths with ou jaune p6.le,parfois incolores, blancs, gris, bruns ir ewaldite, a Sr analogue of ewaldite, mckelveyite, rougeAtres, i poussidre blanche et 6clat vitreux. and rarely with synchysite. Crystals, 0.05 to 2 mm, Duret6 3. Dor" 3.30, D",1" 3.266, Clivage paralldle vary in habit from platy, tabular, columnar, saucer- i la base (plan du facids tabulaire), indistinct ou shaped, barrel-shaped to irregularly granular; they assez bon. Ce min6ral est soluble dans HCI aves are usually pale yellow to yellow, but also colorless, forte effervescence.Observations optiques: cu 1.551 white, grey, brown to reddish brown, with a white - 1.561, 1.646"t 1.652,2V (-) 0-20", X = c*. - P streak and vitreous lustre. Hardness 3. Dore = La donnayite est isomorphe de la weloganite, tri- 3.30 and Dcarc= 3,266 g/cmg. Basal cleavage in- clinique Pl, a 9.000, b 8.999, c 6.7934, q 702.77, distinct to fair. Dissolves in HCI with strong effer- P 116.28, ^y 59.99", Z - L (maille non-convention- vescence.Optically, biaxial negative, with a 1.551- nelle pour montrer l'isomorphie). Pour les neuf p L.561, 1.646, y 1.652,2V 0--20", X = cr'. Don- raies les plus intenses du diagramme de poudre, nayite is isomorphous with weloganite (as shown by 6.103 (4) (001), 4.368 (7)(120, ztl, tr0), 3.209 the following unconventional setting): triclinic Pl, (3)(r2r, r1r, 2r2), 2.839(10) (2lL,rlL r22),2.s98 a 9.000, b 8.999, c 6.7934., a 102.77, p tt6.28, (4)(33I, 030, 301),2.038 (3) (310, 1r3, 2ry,003), y - 59.99', Z t. The nine strongest powder dif- 2.0_18(3) (242, 222, 420), 1.978_(3)_(333, 3Q3- fraction lines are: 6.103 (4)(001), 4.368 (7)(120, 032,032,301,33 1), 1.694 (3) (542, 5L2,140,150, 4rl, ztT, tl,q, 3.209(3)(t2t, tll, 2tZ), z.B3g(10) 45T,214, Maclestrds fr6quentes: par rotation (zLr, 113). rlL r2l), 2.598(4) (33T, 030, 301),_2.038 (3) [103L20";par r6flexion(010), (3OI), (l3l). La sonde (310,r13, 2t2, 00_3,(2j018 (3) (242,222, 420), 6lectroniquedonne Na2O 3.37, CaO 5.75, BaO 1.928(.3) (333, 303, 032,032,301, 331), 1.694 (3) 0.85,SrO 35.8 Yrq 13.1,NdrOB 1.83, LazOa 0.45, (542,5tl, tao, 150,4T1, 4sT,214, tI3). Twin- CO, (30.98),HrO (6.34), total 98.47Vo(on admet ning by rotation about [103]rroo and bV reflection que COz et HzO sont stoechiomEtriques).Cette ana- across (010), (3OT)or (3:t) is extremely common. lyse conespond ir Nao.rr(Cao.s?Ndo.osllao.or)(Srr.r" Electron microprobe analysis gives: Na2O 3.37, Bao.or)Yo.ee(COs)s.3H2O, soit id6alementNaCaSr3 CaO 5,75, BaO 0.85, SrO 35.8, Y2Os 13.1, NdrOs Y(CO3)..3HrO. La mackelveyite,r6examin6e, s'avd- 1.83, La2O3 0.45, COz (30.98), HrO (6.34), sum re triclinique,isomorphe de weloganiteet donnayite; 98,47Vo,CO2 and HzO are assumedto be stoichio- sa compositionoriginelle peut s'6crire (Nat.*Ii.or) metric. The analysis corresponds to Na6.rr(Cae.37 (Cao.zsUo.rz)(Ba2.z2sr0.r7) (Y0.?oREoje) (CO3)0.3.48H2O, Nd6.eel.as.m)(Srr.ssBae.e5) Yo.go(COa)6.3HrO, or ideal- soit NaCaBasY(COs)o.3HrOcomme formule id6a1e. ly NaCaSrgY(COe)6.3H2O. New data show that mckelveyite is also triclinic, isomorphous with (fraduit par la R6dactiotr) weloganite and donnayite; its original analysis may be recalculated to (Nar.rrKn.62)(Cae.7sU o.rr) (Bzr.r, INTRoDUcTIoN Sro.rz)(Yo.zoREo.rr) (CO")..3.48HrO, close to NaCa- Ba3Y(COs)6.3HsO. ln 7973 a specimen from mont St-Hilaire, 'obrockite" Qu6bec, labeled was sent by D. W. Sorvrvrens Richerson to one of us (GYC) for verification. The specimen is composed of arfvedsonite, La donnayite pr6sente pegma- se dans des dykes aegirine, calcite, sphalerite and minor amounts titiques, cavit6s miarolitiques et fissures dans ia of the intersticesof coarse mi- sy6nite i n6ph6line du mont St-Hilaire, dans la catapleiite filling province de Qu6bec. Elle s'y trouve ordinairement crocline crystals.The so-called"brockite" occurs associ6e aux espbces suivantes: microcline, analci- as aggregatesof approximately 0.5mm tabular me, calcite, tratrolite, chlorite, aegyrine, arfvedso- crystals which usually display rough, irregular 335 336 THE CANADIAN MINERALOGIST Frc. 1. Scanning el€ctron photomicrographs of donnayite. (a) Parallel growth or twinned crystal aggregate (1 mm dia.). (b) White tabular crystals (1 mm) of donnayite with brownish-red globular gaidonnayite crystals. (c) Saucer-shapedcrystals (0.2 mm). (d) Columnar (1 mm long) aggregatesdisplaying crystals with pedial termination. (e) Barrel-shaped crystal (1.5 mm long). (f) Hemimoryhic crystals (0.2 mm) with pedial termination. DONNAYITB, A NBW MINERAL FRolvI ST-IIILAIRE 337 and somewhat curved surfaces with an overall and Mineral Names, I. M. A. The tnre speci- hexagonal crystal outline. Some. crystals are mens are deposited at the National Museum of transparent with a pale yellow color but most Natural Sciences, Ottawa (Specimen #39394, crystals show a gradation of color from pale 39395,39396) and the Royal Ontario Museum, yellow and transparent near the rim to dark Toronto (specimen # M35222). reddish brown and alrnost opaque totrard the core. Under high mapification, with a scan- OccunnsNcr AND PrrysrcAr, PnoprnrrBs ning electron mictoscope, each "crystal" was found to be composed of numerous individuals Donnayite occurs in small quantities in the in sub-parallel to parallel growth (Fig. 1a), too pegmatite dykes, miarolitic cavities and inter- small to be separated for single-crystal X-ray stises in the nepheline syenite at Mont St-Hi- work. Preliminary optical and X-ray studies laire, Qu6bec. The mineral is usually associated together with electron microprobe analyses in- with microcline, analcime, natrolite, calcite, dicated the mineral to be a new species, a chlorite, aegirine, arfvedsonite and minel Y-bearing analogue of weloganite (NazSrZr amounts of siderite, rhodochrosite, ancylite, (COg)e.3HO: Chen & Chao 1975, Grice & pyrite, sphalerite, hematite, goethite, pyrophan- Perrault 1975). However, due to the small ite, catapleiite, gaidonnayite and astrophyllite. amount of material available and the lack of Crystals are usually very small, from 0.05 to truly single crystals, a complete description of l.0mm, rarely 2.0mm. The mineral is common- the mineral was not possible and the mineral ly pale yellow to yellow, but also colorless, was therefore tentatively designated UK33. white, grey and rarely reddish brown due to A year later, the mineral was again en- hematite inclusions. The streak is white. The countered in small quantities in varied mineral mineral is transparent with a vitreous lustre, associations, habits and colors on newly col- but the white and grey varieties are opaque ard lected specimens and on specimenssent to us earthy. Crystals with vitreous lustre have a hard- for verification from several advanced mineral ness about 3 on the Mohs ssale whereas the collectors. It became possible, therefore, to earthy material is apparently softer. An in- gather sufficient data for characterizing this distinct to fair basal cleavageis present. Density new species. The mineral has been named don- determined by the flotation method is 3.30(1) nayite, after Professon J. D. H. Donnay and g/cms. The mineral dissolves rapidly in 1:1 G. Donnay, in recognition of their contributions HCI with strong effervescence. to the fields of crystallography and mineralogy. Donnayite crystals generally display apparent Both the mineral and its name have been ap- trigonal or hexagonal symmetry with various proved by the Commission on New Minerals habits from platy, tabular (Fig. 1b), saucer- Frc. 2. Scanning electron photomicrographs of polycrystals produced by syntactic intergrowth of donnayite with other minerals. (a) Hemimorphic polycrystals (1.5-2.0 mm long) of ewaldite (dark bands) and donnayite (hghter bands) with a donnayite 'tay''(D). The polycrystals are white and opaque, the "caps" are pale yellow and transparent. O) A doubty terminated hemimorphic polycrystal (2.0 mm long) of ewaldite and its Sr analogue with "caps" of donnayite(D) and mckelveyite(M). 338 TIIB CANADIAN MINERAI'GIST shaped (Fig. 1c), columnar (Fig. 1d), barrel- X-Rev CRYSTALLocRAPHY (Fig. granular. shaped 1e) to irregularly Some Crystals of donnayite used for the single- crystals are clearly hemimorphic, with curved crystal X-ray diffraction study were first trigonal pyramidal faces converging toward a checked optically for identity and possible in- point on one end and terminated with a flat tergrowth of other minerals using a spindle pedion on the other @ig. 1f). As with the stage and then by X-ray using a 114.6 mm minerals in the bastnaesite-synchysite family diameter Gandolfi camera. The precessionpho- @onnay & Donnay 1953), donnayite common- tographs show that donnayite is triclinic, pseu- ly forms syntactic intergrowths with other min- dorhombohedral and isomorphous with welo- erals of similil strucfure and shemical composi- ganite (Table 1).