Doyleite, a New Polymorph of Ai(Oh)

Canodian Mineralogist Vol. 23, pp. 21-28(1985)

DOYLEITE,A NEW POLYMORPHOF AI(OH)3,AND ITS RELATIONSHIPTO BAYERITE,GIBBSITE AND NORDSTRANDITE* GEORGEY. CHAO ANDJUDITH BAKER Departmentof Geologt, CarletonUniversity, Ottawa, Ontario KIS 586

ANN P. SABINA ANDANDREW C. ROBERTS GeologicalSurvey of Canada,601 Booth Street,Ottawa, Ontario KIA 0E8

associdei calciteet pyrite dansdes filonnets d'albitite dans ABSTRACT la sy6nitendph6linique du mont St-Hilaire (Qu6bec)et d weloganite, cryolite, calcite et quartz dans des sills de Doyleite, a new polymorph of AI(OH):, occurswith cal- silicocarbonatitei la carridre Francon d MontrSal (Qu6- cite and pyrite in albitite veins in nephelinesyenite at Mont bec). Une analysepar voie humide donne: Al2O3 65.290 St. Hilaire, Quebec and in silicocarbonatitesills with (en poids), CaO 0.48, H2O (par TGA jusqu'd 1100'C) weloganite,cryolite, calcite,quartz and other mineralsar 35.76,total 101.44,soit Ale.eCae.el(OH):.00.La doyleile the Francon quarry, Montreal, Quebec.A wet-chemical est inerte dansles acidesHCI I :1, H2SOaet HNO3 a tem- analysis gave: AI2O3 65,2, CaO 0.48, H2O (TGA to p6ratureambiante. Une 6tuderadiocristallographique sur ll00'C) 35.76, sum l0l.M w1..0/0,corresponding to monocristaldu mont St-Hilaire r6vblela sym€trietriclinique; Ale.eeCa6.s1(OH)3.ee.The mineral is not attacked by l:1 son groupe spatialPT est d6termindpqrr sa morphologie, HCl, H2SO4or HNO3 at room temperature.A single- a 5.A02Q),b s.t7s(r), c 4.980(2)A, c 97.50(l)', 0 crystal X-ray study showedthe mineral from Mont Sr. 1I8.60(l)', t lM.74(l)' , ponrZ = 2. Lescinq raies les plus Hilaire to be triclinic, spacegrolp PT from morphology, intenpesdu clich6de diffraction (m6thodedes poudres) [d a s.N2(r),b s.175(1),c 4.980Q) A, a e7.s0(l),B I18.60(l), en A(r)(hkDl sonr: 4.794(100)(010),2.360_(40)(10l), -- 1 104.74(1)",Z 2. Thg strongestfive X-ray powder- 1.972(3q(nD, 1.857(30xll1) et 1.842(30)(r?2).Les diffraction lines [d in A(IX&k/)] are: 4.794(100)(010.y, cristaux, aplatis sur (010), prdsententles formes {010}, 2.360(40X101),t.972(30)(221), 1.857(30X111) and {l0l}, {l0l} et, danscertains cas, {100} et {001}. Ils sont 1.842(30)(122).Crystals are tabular on (010),showing forms blancs, d'un blanc cr6meuxou bleudtre, allant de trans- {010},{101}, {101} and, occasionally, {100} and {001}. parentsou translucidesd opaques,d ralure blanche,d'6clat They are white, creamywhite or bluish white, transparent vitreux, nacr6 ou terne. Duretd 2y, d 3, densit6, 2.48 or translucentto opaquewith a white streak. Their lustre (mesurde),2.482 (calcul6e). Le clivageest padait sur {010}, is vitreous,pearly or dull, Mohs hardness2/z - 3, D(meas.) distinctsur { 100}.Biaxe positif, a I .545(l),0 I .553(l),r 2.48(l), D(calc.) 2.482 g/cmz. Cleavageis perfect on 1.566(l), 2V=77' (Na). Orientation de l'indicatrice {010}, fair on {100}. Optically,the mineralis biaxial posi e:r coordonndes sphdriques (d, p): X(90", 4L'), tive,o 1.545(l),B 1.553(l),r 1.566(1),2V : 77oin Na light. YQ,40",53"),2(343",74), avecc (0,0)et r* (0,900).L'ana- Orientation of indicatrix in sphericalco-ordinates ({, p): lyse thermogravim6triquer6vdle une perte de poids de x(90",41.),-y(2N",53.), Z(i43.,74"), with c (0,0)and)* 25.63V0entre 280 et 4l0oC, et une autre perte, graduelle, (0,90'). TGA showeda weightloss of 25.6390between 280 jusqu'A 1000"C(total 35.76V0).Le spectred'absorption and 410'C, and a further gradual loss to l000oC, giving infrarouge ressembled ceux de la gibbsite et de la nord- a total weightloss of 35.7690.The infraredabsorption spec- strandite, quoique plus simple. On pr6dit la structure de trum of doyleite is similar to but simpler than those of la doylei'tei partir de cellesde la gibbsite et de la nord- gibbsiteand nordstrandite.Its structureis predictedfrom strandite,en sefondant sur desressemblances not6es dans the known structuresof nordstranditeand gibbsiteon the deuxzones sur lesclich6s de pr€cession.Le polymorphisme basisof similaritiesin X-ray precessionphotographs in two r6sultede diffdrencesd'empilement desfeuillets d'octaddres zones.Polymorphism in AI(OH)3 results from different A(OH)6. Le nom rapelle E.T. Doyle, d'Ottawa. ways of stacking the layers of AI(OH)6 octahedra.The mineral is named after E.T. Doyle of Ottawa, Ontarid. (Traduit par la R6daction)

Keywords: doyleite, aluminum hydroxide, new mineral, Mots-clds: doyleite, hydroxyde d'aluminium, mont St- Mont St. Hilaire, Francon quany, Quebec,structural Hilaire, carribreFrancon, Qu6bec,relations structurales, relationship, bayerite, gibbsite, nordstrandite. bayerite, gibbsite, nordstrandite.

SoMMAIRE INTRODUCTIoN

La doylei'te,nouvqlu polymorphede AI(OH)3, setrouve The formerly unidentified mineral UK45 from Mont St. Hilaire, Quebec (Chao & Baker 1979) has been established as a new polymorph of aluminum *Publication 16-84 of the Ottawa-Carleton Centre for hydroxide on the basis of X-ray diffraction, chem- GeoscienceStudies. ical and electron-microprobe analyses and optical 2l

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 22 THE CANADIAN MINERALOGIST

studies. The unknown no. 11 from the Francon pulverulent to compact globules, bolryoidal and quarry in Montreal, Quebec,reported by Sabina smooth porcelainlike crustsand sheetscommonly (1979),has also beenshown to be the samemineral on weloganite,calcite, quartz and lesscommonly on as UK45 according to results of X-ray powder- cryolite and strontianitecrystals. In somecases, the diffraction and electron-microprobeanalyses. The original calciteor cryolite crystalshave been partly mineral is named doyleite after Mr. E.J. Doyle of or completelyleached out, leavingshells of doyleite. Ottawa, Ontario who found the Mont St. Hilaire The mineral is generallyadmixed with unknown No. material. The mineral and its name have been 3 (Sabina1979), believed to be an aluminumhydrox- approvedby the Commissionon New Minerals and ide with an X-ray powder pattern similar to that of Mineral Names,I.M.A. Type specimensfrom Mont gibbsite.Other associatedminerals are albite, dres- St. Hilaire are depositedin tho collectionsat the serite, dawsonite,fluorite and analcime. National Museum of Natural Sciences,Ottawa, Ontario (NMNS 48932) and at the Royal Ontario CnvstalrocnePnv Museum, Toronto, Ontario (M41025). Specimens from the Francon quarry are preservedat the Geo- Eight crystalsand crystal fragmentsfrom Mont logical Survey of Canada, Ottawa, Ontario. St. Hilaire were studied by single-crystalX-ray diffraction using a precessioncamera with various OccunnsNcs zone-axesof the crystalsas the precessionaxis. The photographs show doyleite to be triclinic, space The mineral occursat Mont St. Hilaire asrosettes group Pl or PT. The centrosyrnmetricspace-group of platy crystals (Fie. l) lining a wg in a vein in is suggestedby the morphology of crystals. The nephetne syenite.The matrix rock, albitite, is almost reducedcell wasestablished in a computersearch of wholly composedof albite with lessthan 590 side- the shortesttranslation vectorsin direct space.The rite and minor amountsof pyrite, molybdenite,zir- cell parametersobtained werethen refined by a least- con and fluorite. Within the vug, the only associated squaresmethod using Gandolfi X-ray-diffraction minerals are calcite and a small amount of pyrite. data. The refined cell-parametersand X-ray powder The doyleitecrystals are in placescoated with a thin data of doyleitefrom Mont St. Hilaire and Francon film of dark brown amorphousmaterial, probably are comparedwith those of other polymorphs of iron oxide. Some doyleite rosetteshave a core of A(OH)3 in Tables I and 2. The reduced cells of albite. Underlying the doyleite rosettesthere is a nar- doyleite and nordstrandite are usgd in Table I to row (l-5 mm) but distinct reaction-zone,suggesting accentuatethe differencesin cell geometry of the that doyleitewas depositedfrom a later generation polymorphs. of fluids after the emplacementof the vein. Becauseofthe presenceof a perfect{010} cleavage At the Francon quarry doyleite occurssparingly the conventional Debye-ScherrerX-ray powder- in vugs in silicocarbonatitesills intruding Ordovician diffraction pattern shows a strong preferred- limestones.The mineral is finely granular, forming orientation effect that causesvariations in relative intensitiesof the 0k0 lines.The 020reflection, which has a low to medium intensity on the single-crystal

l@s l. Gu Pm M mlru ,@Tla ot llqlw tltlMloE Nl||&s

0) (2) (rl byt€lre Dqlotte kdshndlto ol&lb nlrlcl Inl. &tdlto hYdr!.g! | | lion

! (8) 9.@2() 9.OA(g) 6.14(2' 8.@rlt l7.rs ,.@2ltt t.17r( tl ,.17711t 6t9$(2) '.0?81 t' 10.@ a,67lt2t 4.9S(2) ,.060) ,.074t1, 9.?$(1, 9.7! 4.711(l) 97.50(t) 97.90C) 9r.1612' s.t? B I10.@tr ) |9.S02) S.@12) g.A (l) 9.1! N.21 (3t Y 18.?4( t) l&.000) 8r.rol2) e.00 v (8!) 1o4.52ttt lor.i() 2r.1711) 429.0 t6q.o &.s

2224At24

pr_

2.44() 2.42 2,40 2,142 2.4X 2A 2.y

l.!5( | )(tr.) r.$0(l)(la) r.!8 B r.rrr(r ) t.ts0l l.s T t.s6(t) r.&2t l) t.f? (+124. (+) O. 21.40.

(l) ht siHll!!r3, Qlabc, thle stldt. (2) Frln@n qlarry' bh4l, Q!6s., thl3 etldt. l. Doyleite crystals(0.8 x 0.8 mm) from Mont St. (1974). Frc. (r, lonl st Hll!1.o, ou.b, ch6 & &kr (t9ul. (4) Ssatt.ld & f6dd6 0ptl6l Hilaire, Quebec. or@tler tr@ Pllsd..i.l. (lqa). (r, !.ttord (lso). (6) to1h&u6r d !1. (l$7t.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 DOYLEITE, A NEW POLYMORPH OF AI(OHh 23

t&E 2. X-Mt tuNl,lffitd D r F@ mElE, @tutE, OtsSlE @ *thlt

oqlelt€ !d6f&dlb ct&tb &6lb

hkr d@rcl ddJ I ddJ har i&l r hkt ddBl I nat aoJ ,

010 4.n9 41* to 4.0@ to rc 4.U9 r@ @ 4.S '20 6l {.?t 90 ld 4.2tr 4.M 20 4.n 6 lrc !.,? to |to 4.J7 to |o 1.tt 70 @ {n, 4n& 20 1.16 2 o11 4.24 20 2@ 1.' A @O @ 4.AO 4.67 20 1.1@ 2 to 4.1@ , ti2 ,.& t6 dl !J4 2 ilo !.& r.@ 1a t.41 2 ofr ,.0$ to 112 t.ta7 12 120 t.n 2 ol ,.r4, ,.16 1t t.142 2 ro ,.6@ to 1oJ ,nr2 I ltl a.2a to 1tr '.'6 J.2 lt t.t8 2 @o t.1a t a1 2.64 6 @tr llt 3.@a J.@ to ,.@t I 2@ !.O9 t @ 2.40 20 121 011 2.7& 2.7n t 2.711 ' 121 2.82 ' alt 2.8 2' 26 2.atl 2 f 1 2.12A 2.110 I 3!r 2.7@ t tt2 2.At 6 tro 2.rto 2 211 2.4t 2.A 20 2.& 4 !21 2.9 10 @ 2.24 l0 OJt 2.@ 2 @o 2.@ 2.rs I 211 2.41 a 215 21O 2.4\ 2 16 2.t9 2.yO 40 2.N2 6 uo 2.a9 4 t12 2.1@ 6 @ 2.M 4 t2 2.r2t 2.tu 20 2.t27 t 112 lu 2.@ 2 d2 2.274 2 221 l.m 1.92 io l.s9 , 2Jl 2.t2t | 3il 2.q, t6 2ot 2.m t@ I X t.8rt l.s7 s l.s, a 211 2.26t 40 @t 1.* t2 l'+ 14 1.42 1.A2 to r.@ , lt 2.219 I l2J l.$O 2 UO 2.16 2 o12 1.1t t.lt I ot1 2.111 a 111 1.Al t2 dO 2.1@ 2 ao t.67, r.@o I 14 2.112 | 'i4 t.E t4 2tt 2.164 2 2! t.@ t.6, t t.6r I 212 2.@' ' @4 1,1a0 16 211 2.16 2 lt2 l.& 112 al4 t.@ 11 il2 2.@t 2 ?z 1.0$ 1.619 r0 t.62, 2b 6t z.ott lo zi t .azt 4 @+ 5U l.6ta ,1 o i.sJ I a2i t.6r 2 t1o t.r, 2 1.6 1! r.rr , l.at t @ 1.94 X 221 r.rg 1 21 t.*t { 2to 1,ra r.t 2 1 z2 1.W t0 tl1 @t l.s9 2 ?01 l.r4o i.t@ , l.r4t I 191.net9t.2u2122 t.917 2 2t1 1.aU l.r1d r0 r.t! tb s t12 2tA r.9d 2 u1 1.a1a @ 1.16 1 2tO 1.a1, a I4i r.89 2 Francon quarry, Montreal v 1.4r r.@ I l!2 1.6S 2 ,o 62 l.e6 2 Fro. 2. Doyleite from the trc l.at9 t.4s lo t.4! 4 {J a@ l.rr5 2 2t1 1.7@ 2 m 1.4tt 1.6t0 Island, Quebec.Scale bar l0 pm. l4l 7 2tt r.ra1 2 2@ 1.6 ro t2o 1aa 1.48 It l.4t I ry 1.tq r l.@ 2 ltu ,o 1.46 ?2 1.1n 2 '2 r.@ 2 ,D i.S t.rt ro l.:9 2! 1r? 1.111 2 1.L7 10 212 t.@ 2 gr t.r6 1n t.4t 6 'o 1.6$ 2 l1l 1.27A 1.27A r0 r.?70 tb 141 l.9o t t.4@ 6 26 1.@ 2 1' 1.%a l.6a 1O r.240 lb .11 l.rtl to 1.rS 6 Ito r.6ar 2 crystalsto be platy with pointed terminations 1@ @ig. 1.2@ t.2@ , 14t l.9o 2 @1 1.6tu 2 4t 1.2@ 2D l.4m to i.$1 1 m 1.60 t0 2), resemblingthe common habit of nordstrandite zf,i l.t$ tn5 , 1.2@ 2b t2 1.@ I l.to 2 w l.i& ,1' I r.rro 2 t2o 1.t2 2 (Chao & Baker 1982). 1.162 I j'o l.ax l, l.l2o 4 @ lp 1,25 2 all 1.5t1 A 1?2 1.211 4 t1r oz r.@ 2 112 1.123 2 PHYSICALAND OPTTcALPnopsnttrs $t t.s 1 r42 rr9 r.rro r gi 1.19 2 gz2 Doyleite from Mont St. Hilaire is colorlessand ?!r r.:r t 2t2 222 OA 14 l! transparentto translucent,with a vitreousto pearly 2t1 t.I' 5 @ lustre t52 Ztu and a white streak. The mineral from the Fran- e! f.2& t ta @1 12t con quarry is white, creamywhite or bluish white, g14 @2 1.91 2 9t t-a . !!l l.tQ 6 translucentto opaquewith a dull lustre. The Mohs g|2 r@ lta ,,i, ! 6l l.$t 2 hardnessis about 2Vzto 3. The density of doyleite !1 g! 4{q 2r1 t.r7o 2 from Mont St. Hilaire, determinedby flotation in t2l f.19, a ?1 t1o tt2 a heavyliquid, is 2,48(l) g/cm3, in good agreement 152 l.1S 2 Pl!.2t t.t2a with the calculated density of 2.482 g,/cm3.The crystalplates are slightly flexiblebut not elastic.The r. dddrdt6, l. t.ajd, |4.6@a!tutrt @&,6 st !! tntd.r.&rd, rl&.1 r mineral is not fluorescentin long- or short-wave 2. Ud r.drdl6, l r.!td, [a.6 @ Dqe9 vrul rnrdtrr6. h.€ ilE e, 'r" I 0.6", 2.5r lnd 2..'or) ind€-br. o tu b,r6 6, ft€ :I;illJ;i: ultraviolet light. It is not solublein l:1 HCI, HrSOa t. tu3&ir (t€2). or HNO3 at room temperature. In addition to a .. rndr6 be @ th6 Pjln 6rr, . r 6.69, b r r.or, c - 9.?oll, B - 9.j2'. J. 5Fr6l., d €t!€ eldt.td t.6 €tt dtdrr6! tlbt€ tr, !lg@ tq [6! rtin @ttto,. perfect {010} cleavage,a much lessdistinct {100} cleavagehas been observedon some crystals. Optically, doyleiteis biaxial with a 1.545(l),B photographs, is either absentor too weak to be meas- 1.553(1),r 1.566(l),2V : 77" (meas.),76.8o(calc.) ured on the Gandolfi photographs but is always in Na light. The orientation of the indicatrix, with presenton the Debye-Scherrerphotographs; its rela- respectto [001] and (010),is shownin Figure 3 and tive intensity varies from 5 to 20. is defined by the spherical co-ordinates (S,g) The crystals of doyleite from Mont St. Hilaire X(90",41"), Y(240", 53"), 2(343",74') with c(0,0) (Fig. l) aretabular on (010)and boundedby {l0l} and b*(0,90"). In white light the mineral shows and {101} pinacoids,giving rise to a nearly square moderatelystrong dispersion,r > v. outline. On somecrystals the {100} and {001} pinacoids are also present,modifying the shapeof the CHEMICAL COMPOSITION platesto different degreesdepending on the promi- nence of these forms. A centre of symmetry is A hand-pickedsample of doyleitefrom Mont St. apparent. Hilaire was leachedwith weak HCI to removethe The material from the Francon quarry is very fine iron-oxide coating on somegrains and analyzedby grained. The scanning-electronmicroscope shows the conventionalwet-chemical methods for major ele-

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 24 THE CANADIAN MINERALOGIST

TABLE3. COMPOSITIONOFDOYLEITE

Al 203 64.8 63.7 63.f 65.2 59.6 65.36 5i0r 0.03 0.t2 3.22 Ca0- 0.01 0.48 nta lilg0 0.96 Fe0 0.16 0.14 0.21 0.08 Na20 0.08 0.09 0.06 0.35 Hzo 35.76 Jl. /o Jt. /o Ja. /o 35.56 34.64

Total 100.81 99.72 99.25 101.44 100.00 100.00

analyses by P. Jones. H20 by TGA. 4. f,lontSt.Hilalre, Quebec. l{et-chemicalanalysis by Bondar- Cleqa& Co. Ltd. Hro bv TGA. 5. rranc6i quarry, I'lontrEal,Quebec, Averageof four electron-nicroprobeanalyses by I. Bonardi, GSC. Coffectedagainst gibbslte lnternal standard. H20by di fference. 6. Calculatedfor theoretlcal A1(0H)3.

Mont St. Hitaire show that the dehydrationbegins at about 200'C:,the maximum rate of dehydration occursbetween 280' and 4l0oc, with a weightloss Frc. 3, Opticalodentation of doyleite. of 25.63t/oat 425oC. Thereafter, the dehydration continues at a much slower rate, leveling off at 1000'C.The total weight-lossat I100'C is 35.7690. ments. The water content was determinedby ther- On cooling from 425"C to room temperaturethe mal gravimetric analysis to l100oc. The results partly dehydratedmineral regainssome of the lost (Table3, no. 4) correspondto Alo.eeca0.or(OH)3.00.water, giving a net weight-lossof 1890, approxi- The Mont St. Hilaire material was also analyzedby mately one half of the water in the mineral. X-ray electron microprobe using a seriesof ten-second diffraction showsthe partly dehydratedmaterial to counts,a defocusedbeam, and natual gibbsite(Al), be essentiallyamorphous, with faint dilfuse linesof anorthite (Ca), albite (Na, Si) and olivine (Fe, Mg) 7-Al2O3,indicating a completedestruction of the as standards.K and Ti werelooked for but werenot doyleitestructure and commencementof the forma- detected.The Francon material was analyzedby elec- tion of 7-Al2O3.The final product of dehydration tron microprobeusing a broad beamand a moving- quenchedfrom ll00oC is 1-Al2O3in three casesbut sampletechnique with syntheticcorundum (Al) and it is corundum with a trace of an unidentifiedphase kaersutite(Si, Ca, Mg, Fe, and Na) as standards. in another. The sampleused in the latter analysismay Resultsof four analyses,corrected against that of have been slightly impure. a natural gibbsiteinternal standard,were averaged. The infrared absorption spectrumof doyleite from No other elementswith Z > 1l were found. The Mont St. Hilaire is comparedwith that of nordstran- water contentof the Franconmineral wasnot deter- dite and gibbsitein Figure 4. The spectrumof doy- mined owing to the small amount of pure material leite is characterizedby its simplicity in the OH- available. The electron-microprobedata are com- stretching(3300-3700 cm-r), OH-bending(700-1 100 pared with the resultsof the wet-chemicalanalysis cm-r) and AlO-stretching (200-600 cm-r) regions. in Table 3. The differenceis attributable to the fact that there The Gladstone-Dale calculations (Mandarino is only one crystallographically independent 1979),using the resultsof the wet-chemicalanalysis AI(OH)6 octahedron in the doyleite structure, normalizedto 10090,gave Kp/Kg:0.223/0.253 whereas there are two in the nordstrandite and : 0.881.The large discrepancybetween Kr and K6 gibbsite structures. could not be accountedfor by experimentalerrors in the chemicalanalysis or measurementsof indices Srnucrunel RpLattoNstltP to of refraction and density. It is possiblethat struc- Ornnn A(OH)3 MtNPnars tural configurationssuch as packing and hydrogen bonding may play an important role in this case. Doyleite possessesa perfect cleavage,which is common to the other AI(OH), minerals, for THSRMAI- ANALYSES AND instance,{001} in gibbsiteand {110} in nordstran- INFRARED ABSoRPTIoN SPncrnurra dite (Chao & Baker 1982).Although cleavagein natural bayerite from Hartrurim, Israel (Gross & The TGA and DTG analysesof doyleite from Heller 1964)was not reported,Debye-Scherrer pho-

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 DOYLEITE, A NEW POLYMORPH OF A(OH)3 25

.9 .9 E c o F

38 36 34 32 30 28 26 24 22 20 19 l8 17 16 1s 1/ 13 12 r',r 10 9 8 7 6 5 Wovenumber cm{x100 Frc. 4. Infrared absorption spectraof doyleite (a), nordstrandite(b) and gibbsite (c).

tographs of synthetic bayerite show a strong e atomic co-ordinatesof doyleite can be predicted preferred-orientationeffect for 00/ reflections,sug- from the atomic co-ordinatesof nordstrandite (Roth- gestingthat a perfect {001} cleavageis alsopresent. bauer el al. 1967)to two decimalplaces with confi- Furthermore,the Glevelb-precession photograph of dence. doyleite is nearly identical to the 0-level tll0l- Similarly, the OJevelI l0l]-precessionphotograph precessionphotograph of nordstrandite, and both of doyleite is nearly identical to the 0level c- are very similar to the c-precessionphotograph of precessionphotograph of nordstrandite and the gibbsite.Therefore, there is little doubt that doyleite 0Jevelb-precession photograph ofgibbsite. Thusthe also has a layered structure with the layers of projection of the doyleitestructure along [l01] must A(OH)6 octahedra essentiallysimilar to those in be almost identical to that of nordstranditealong c gibbsite (Saalfeld & Wedde 1974), nordstrandite and that of gibbsitealong b. Therefore,they atomic (Saalfeld& Jarchow 1968)and bayerite(Yamaguchi co-ordinatesof doyleite can be determined. The & Sakamoto1958, Rothbauer et a|.1967). Hence, structure of doyleite so derived is shown in Figure the structural relationship of doyleite to other 6, whereit is comparedwith that of bayerite,gibb- AI(OH)3 mineralscan be deducedfrom the geome- siteand nordstrandite.To facilitate comparison,all try of its unit cell in relation to the cellsof other poly- structuresare shown with respectto a gibbsite-like morphs: This is shownin termsof the structuralcell cell, with the projectionsmade along the rxes cor- of gibbsitein Figure5, wherethe pseudotrigonalcell respondingto d of gibbsite. of bayerite(Montoro l942,Yasngtchi & Sakamoto The polymorphism in A(OH)3 is a result of 1958)is shown by dashedlines and the true mono- different ways of stacking octahedral layers, as clinic cell (Rothbaueret al. 1967)is approximated shownin Figure 6. In bayerite,each layer is stacked by the gibbsitecell with q and b interchanged.The directlyabove the layerbelow. In gibbsite,the stack- doyleitecell is shownby dottedlines. The nordstran- ing is similar to that in bayerite, but every second dite cell is approximatedby that of gibbsitewith a layer is turned upsidedown, creatingz-glide planes and b of gibbsite correspondingto [T0] and -c, and 21 axesbetween the layers. In nordstqandite, respectively.Based on the near-identity of the ,- the successivelayers are displacedby 1.70A along precessionphotograph of doyleiteand the [110]- -b of gibbsite, whereas!n doyleite the successive precessionphotograph of nordstrandite,the x and layersare shifted by 1.95A along D of gibbsite.The

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 26 THE CANADIAN MINERALOGIST

bs-5.oA

r\ C' t'/_____ (d

Gn------>

Frc. 5. Idealizedstructure of gibbsite projected on (001), showing geometricrela- tions of the cellsof gibbsite(solid lines),bayerite (dashed lines), doyleite(dotted lines)and nordstrandite.Subscripts: g for gibbsite,d for doyleiteand n for nordstrandite.The oxygenatoms are at heightsof 0.1I (shadedlarge circles) and -0.1 I (unshaded).

shifts of the layersin the directionscorrgsponding hedral layers are possible; for example, displace- to a of gibbsiteare r^elativelysmall, 0.53 A in nord- ment of successsivelayers along a or - a of gibbsite strandite and 0.32 A in doyleite. or mixed doyleite-nordstrandite,doyleite-bayerite Theoretically, other schemesof stacking the octa- and nordstrandite-bayerite layers are possible.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 DOYLEITE, A NEw POLYMORPH oF A(OH)3 27 7\il

(o -l\, (o (\l (f) !--- = ffi\t;tllllH 1 \ III| l'- o oi tl ll o o ol I I I I I I ::-- I I i\z /\1 tR- _, t, *8=5.06 A* *b=5.028 A* (a) (b)

:_5\ t ffi \il, 7\t ffit I I I \ I I I I I I N o) I I I I I ll o) I I @ tl '//k -; ,o I I o' I I ol F @

I I tt t t//, -\

*c= 5.O74 -[i 0i]=5.096 (c) (d)

Frc. 6, Idealized structuresof (a) bayerite, O) gibbsite, (c) nordstrandite and (d) doyleite viewed along a' of the gibbsite- like cellswhich are relatedto the respectiveadopted cells (Table l) by 010/100/002,lM/010/001, I 10,/001/ll0 and tOltTOIttZt. Shadedoctahedra are approximatelyat heights of 2/6 and 4/6, unshaded,l/6 and 5/6.

"Triclinic hydrargillite" (Saalfeld1960), which has for critically readingthe manuscript, P. Jonesand largevalues of a and b, could perhapsbe explained M. Bonardi for electron-microprobeanalyses, D.A. by such mixed layers in an ordered arrangement. Walker for a SEM photomicrograph (Fig. 2) and ProfessorH. Saalfeldfor providing precessionpho- ACKNOWLEDGEMENTS tographs of his "triclinic hydrargillite" for comparison. This study is supportedby NSERC grant The authorsthank Drs. R.C. Erd and E.E. Foord A5113to G.Y. Chao.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021 28 THE CANADIAN MINERALOGIST

REFERENcES Saelrelo, H. (1960):Strukturen von Hydrargillit,Ent- wasserungsmechanismusund Struktur der Zrvischen- Cueo, G.Y. & Baxnn,I. (1979):What's new from produkte.Neues Jahrb. Mineral. Abh.95, 1-87. Mont St-Hilaire,Quebec. Mineral. Rec. 10,99-101. & JancHow,O. (1968):Die Kristallstruktur von & - (1982):Nordstrandite from Mont St- Nordstrandit, AI(OH)3. Neues Jahrb. Mineral. Hilaire, Quebec.Can. Mineral. 20,77-85. Abh. t09, 185-191.

Gnoss, S. & HEr-r-rn,L. (1964): A natural occurrence & Wspos, M. (1974):Refinement of the crys- of bayerite. Mineral. Mog. 33,723-724. tal structure of gibbsite, AI(OH)3. Z. Krist. 139, t29-r35. MaroanrNo, J.A. (1979):The Gladstone-Dale relationship. III. Some generalapplications. Con. Mineral. SenrN,q,A.P. (1979):Minerals of the Franconquarry t7.71-16. (MontrealIsland): a progressreport. Geol. Surv. Can. Pap. 79-lA, 115-122. MoNrono, Y. (1942): Structura cristallina della bayerite. Ricerca Sci. 13, 565-5'lI. YaueoucHr,G. & Saravoro,K. (1958):Crystal structure of bayerite.Chem. Soc. Jap. Bull. 31, 140-l4l. Perecue, C., Brnuar, H. & FnoNpn, C. (1944): The System of Mineralogy I (7th ed.). John Wiley & Sons, New York.

RorHsauEn,R., Zrcar, F, & O'DeNrsr-,H. (1967):Ver- feinerung der Struktur des Bayerits, AI(OH)3, Einschliesslich eines Vorschlags fiir die H- Received May 30, 1984, revised manuscript accepted Positionen. Z. Krist. 125. 317-331. July 10, 1984.

Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/23/1/21/3435235/21.pdf by guest on 28 September 2021