TWO YTTRIUMMINERAIS: SPENCITE AND ROWLANDITE1

CLIFFORDFRONDEL Haruar d, Univ ersity, Cambr,i.d,ge,M assachusetts

Assrnecr Spencite is a new borate-silicate of calcium and yttrium, (Ca, Fe)2(Y,La)a(BaSin.aAl.z)s(O, OH, F, Cl)20 fro11 1 pegmatite in Cardiff township, Haliburton County, Ontario. Found as dark reddish brown to brownish black anhedral masses.Hardneis B$, specific gravity 8,08. Metamict; isotropic with n near 1.630. when the mineral is heated at 925" i the n increases to about 1.640 and the specific gravity to 8.20. At high temperatures the mineral decomposesbefore it recrystallizes and r-ray difiraction daticannol be obtained. spencite is related chemically to the minerals of the Datolite Group and may be iso- structural with them. It is named after the canadian mineralogist Hugh s. Spence. A re-examination of the little known mineral rowlandite from Baringer Hiil, Texas, establishesit as a valid species.Composition near (y, Fe, Ce)s(SiOa)r(F,0H). Metamict; with n 1.704. Hardness 5$, specific gravity 4.Bg; *-ray powder data are given foi material recrystallized in nitrogen at 900" c (with tnean n 1.76, specific gravity a.65).

Spsxcne This new mineral was collected by Hugh S. Spence in 1gB4 from a prospect pit in Cardiff township, lot 7, concessionXX, Haliburton County, Ontario, and was tentatively identified as thalenite. It occurred as massesin a narrow pegmatite stringer in a vuggy pyroxenite, associated with calcite, red apatite crystals, diopside, purple fluorite, and wernerite, about 200 feet from an outcrop of normal reddish granite pegmatite. About 24 pounds of pure material were obtained, including a single mass weighing 8 pounds that apparently was a fragment of a single crystal. cracks in the mineral are filmed by a fine-grained white carbonate that is high in yttrium. spencite is dark reddish brown to brownish black in colour, translucent in thin splinters, and has a weakly vitreous lustre. The powder is greenish grey. The mineral is metamict and isotropic. The index of refraction varies betweenI.627 and 1.653with the bulk near 1.680.The colour in transmitted light is pale olive-brown to yellowish brown. The hardness is 3$ and the measured specific gravity is 8.0b. When heated in air at 325'C for 46 hours the average index of refraction increased to about 1.640and the specificgravity to 3.2A; the material was still isotropic and did not give a diffraction pattern. lContribution from the Department of Mineralogy, Harvard University, No. 400. o/o SPENCITE AND ROSTLANDTTE 577 A quantitative chemical analysis, carried out in unusual detail by c. o. Ingamells, with supplementary deterrninations by others, is cited in Table 1. The analysis sample weighed 1b grams. It had been treated T"""r l. C"r,rt"* 1"**tt

Na2O 0.11 .0018 0.037 KO 0.01 .0001 0.002 Mgo 0.50 .0L24 0.127 CaO 7.81 .1393 1,.424t2.05 SrO 0.05 .0005 0.005 FesOe* 3.22 .m2 o.4L2 MnO 0.60 .0084 0.086 YOaf 28.20 .LL24S 2.554 CegO: L,M WM Larosl 4.16 0128 33391' * Tho, 2,M .0092 0.094 ALOa$ 3.87 .0380 0.777 TiOe 0.27 .0034 0.035 BzOall 10.04 ,LMz 2.949f8 sior' 24.89 .4LM 4.237 &Oo 0.02 .0001 0.o02 cl 0.45 .oL27 0. 130 F o.M .0232 0.237 HrO+ 9.82 Oxygen atoms : 20.7 HrO- 1.93 (HrO, F, Cl excluded) Total roo.27 LessO:F,Cl 0.28 99.99 tTotal iron reported as trivalent, but betieved to be present in tne non-metamict mineral as divalent and so treated in the deilved formula. -lX--ray spectrographic analysis indicates that the other rare eartls ol the yttrium group are present only in very small amounts (chiefly Gd, Er, Ho). IX-ray spectrographic analysis indicates that other lanthanide ele- me-ntsare prgselt. only in small amounts (chiefly Nd). $IncludesBeO in undeterminedbut quite smill amount. llA confirmatory quantitative spectros;aphic analvsis bv H. Bastrom of the U.S. Geological Survey eave 10.0-B3Os. Norn: Examination by opi=ical and *-ra! spectrographic methods showsthe presencein traci:amounts of U, Sn, Cu, Ni, C6, pb, Zr, and Sc.

by heavy liquid and magnetic techniques, which removed traces of foreign matter, and under ttre microscope appeared homogeneous. The mineral doesnot afford a distinct r-ray powder diffraction pattern, either unheated or when heated near to the point of apparent chemical de- composition, and tJris has hindered the interpretation of the systematic crystallochemical relations. 'Basically;,spenciteis a borate-silicateof calcium and yttrium. Since the main cations are large in size, the analysis was calculated on the assumption that the subordinate small ions Al and Ti were part of the 578 THE CANADIAN MINERALOGIST anionic framework together with Si and B. The trivalent rare earths together with Th, andlhe divalent cations together with iron as Fe2and Ni were grouped separately. In this basis, virtually whole number ratios were obtained when the total of small ions (Si, B, Al, Ti), was taken as 8 (Table L), and the formula may be written (Car.soFe.asMg.rrMn.osNa.oa)s(Yz.roCe.osLa.:oTh.os)3(Sia.zaBz'erAl'ra'fi'og)a (On.zrOHr.azF.zaCl.rg)zo

In this formula the total of divalent cations has been adjusted to 2 from the calculated total of 2.09. The content of HzO is uncertain' The analysis indicates 5HzO, but metamict minerals commonly contain much secon- dary water and the actual amount of essential H2O present, doubtless is less than 5HzO and may be nil. When heated at 325oC, the mineral loses76.0 per cent of the total Hzo present (11.75weight per cent). The irrational content of (F, Cl) indicates that (OH) must be present' The composition suggeststhat the mineral may be structurally related to the Datolite Group-(Table 2). In this group, the isostructural relation of datolite to herderite was recognized,byStrunz (1936). The relation of TeaLB 2. MBMsrns oF TEE DanolrrB Gnoue

4o bo cs Beta Unit cell contents (A) (degrees) Reference (1953) Datolite CaeBe(Sioe)a(oH)n g.62 7 .60 4.84 90 9 Ito & Mori Bakerite Ca4B(SisBr) s,B7 7.57 4.74 so 22 Ten4vson,instru)nnyson, in Struuz Homirite (1e5?) ""!&8fJt'Jf".8]o (1'936),Pavlov & Herderite caBen(Poa)a(oH'F)4 9.82 7.70 4.81 90 6 Stninz Belov(1967). ,.-- (194O) FerYrBea(Sior)Oa 9.89 7.55 4.66 90 Brandenlierger Gadolinite (1959), Milton Garrelsite Ba*Be(SizBr) Christ (o,4(oH)'xoH)4 et al'. (1956) Spencite (?it;Ilol8'i,*8i,

Nore: Spacegroup P 21/a

datolite to bakerite and homilite was establishedby Frondel (1947) and later, with the inclusion of gadolinite, by Ito & Mori (1953).The structure of datolite as described bV the latter authors is composedof complex sheets composed of interlinked (SiOa) and (BOaOH) tetrahedra with by the composition [B$iro8(oH)r]. The sheets are bonded together ca ions coordinated with six oxygensand two (oH) groups. In herderite' Be replacesB and P replacesSi. In gadolinite, as shown by Ito & Mori (1953),Ca is replacedby Y, B by Be, (OH) bv O, and in addition two ie2 ions enter the vacanciesat 0, 0, 0 and O, Lfz, l/2 irt the unit cell' SPENCITE AND ROWTANDITE 57g ln bakerite, one of the four si atoms in the celr is repracedby B, with a concomitant substitution of an (oH) for o in its ioordinaiio' group. The composition garrelsite of has been discussedbv ctrristldgbg), who also corrects the formula of bakerite as earrie, *ritt"r, by Kramer & Allen (1956)and Frondel (1gaz).Garrelsite, however, is notisostructural with the Datolite Grgup although, like spencite, it is related chemicalry to the minerals of this group. The formula of spencite can be recast in the structural form of the Datolite Group as follows (Car.aoFe.asMB.rzMn.6r|tra.0r)r(Yr.oeCe.osLa.zsTh.os)g(Bz.grSir.ozTi.os)a ( (Sir.zrAI.zr)Oa)a(O2.;rggrezF.zCl.rr)e This requires assigning Si1.e2or (Al.?BSi.r4)to boron positions and leaves one..of the cation positions vacant. The vacancy may be in the g-co- ordinated Y positions, as written, or in a 6-coordinated ca position (the Fe positions in gadolinite) with the two cation fo.itiorr" tt occupiedas Ca(YaCa)a. "r, spencite differs significantly in composition and ratios from other known borate-silicates and in any case stands as a distinct chemical entity. cappelenite, essentialrya borate-silicate of barium and yttrium, has Y:B - 1:1 and - B:Si 2:l.It has a hexagorul*orfhology, arrd and x-ray powder pattern does not closely t"r"-bl" either datorite or apatite. Melanocerite,caryocerite, and tritomite, all probably d;ri;;;i";; of the apatite structure, have ce as the dominani rare-earth and are relatively low in B. steenstrupine, a rhombohedral pho"pt ui"-silicate of (ce, La), ca and Na chiefly, lacks B but containsa small amount of Be. yttrium The silicates, thalenite, yttrialite, and rowlandite (redescribed beyond), are not related to spencite. Stillwellite, ideally C"gSiOu, ,rruy be a cyclosilicate with tjre structural formura ceu(Bso;)(siuorj, as sug- gested by Strunz (1952). The mineral is hexagonarand its r-ray powder pattern (Gay, 1957) does not resemblethat oidatolite. unheated spencitedoes not give a distinguishabler-ray powder pattern. The metamict material is unstable thermalry, and i".o*por"" ut u relatively low temperature' apparentry in the range 450-b;0'c. un- fortunately this is below the rangeof temperature at which most metamict silicate minerals recrystalize at an appreciablerate, and it has not been possible to obtain useful ,-tuy po",der patterns. Heated in nitrogen at 7!0 900'c a light-coroured, ?''d porous to sraggymass is obtained; at 1050' c a yellowish white, sintered masswith . riir"ou" lustre is formed, that contains small bubbles. The r-ray pattern of the latter materiar is given in Table B, and has not beenidentinea. 580 TIIE CANADIAN MINERALOGIST Pnooucr or TeeLE 3. X-neY Powpsn Specrr'rcO#1:ffiO"wLANDrrE lNo Hoerrnc

SPenciteOi$uct Rowlandite I Id I d 2.MS 11 4.87 59 2.608 37 4.N I 2.522 34 4.05 22 2.O29 10 4.32 1l 1.934 19 3.90 26 2.MO 33 3.86 18 , 2.28 8 3.41. 18 1.882 3.59 54 1.829 36 AI 2.r22 27 3.27 t2 3.51 1.799 23 3.29 15 2.076 47 3.14 22 2.01() 8 3.07 29 L.773 18 3.r4 12 t.7M 23 3.06 100 2.000 10 2.96 24 .>, r.704 10 3.01 1.957 15 2.801 100 2.89 3I 1.911 2T 2.760 t7 34 2.AO 15 1.803 I11 2.708 2.779 t L.764 18 2.629 12 2,,656 20 L.7n 42 2.2M 10 -1.b418. intensity in arbitrary chart @er, tr Relative units. Rowr-euortB E' The yttrium-silicate rowlandite was described in a note b;r W' aside Hidden-in 1891 and no further information has been published, fromaremarkbyF:L.Hess(1908)thatitcontainsSpercentfluori.ne. yttrialite The mineral was fourrd as smali irregular massesassociated with Texas' and gadolinite in the pegmatite at Barir'rgerHill, Llano County' in thin Hidden stated that it wis pale drab greertin colour, transparent analysis splinters, with a specific gravity of 4515. A partial chemical gurr" (Y, etc.)zoso1.gt,'plo a.6g, Cao 0.1"9tUou'0'40, Sioz 25'98' ign' wealth io"" Z.bt, total gb.L8.Tire Baringer Hill pegmatite, in spite-'ofthe by of unusual minerals that it afforded, is very poorly represented speii- 'specirnen here mens in the leading reference collections' The" ^ypi a specialist examined*u, pr"r"ri"d in the collection of the late O' I' Lee' of in the rare earths, who obtained it from w. D; Niven,'an associate Hiddeninthestudyandcommercialdevelopmentofthe.Baringertlill pesmatite in the peiiod 138?-1907.Summary accountsof tfrg mineralogy (1932)' of lfr" pegmatite are given by Hess (1903) and by Landes gravity The mineral is melamict and isotropic, with'i'.1.;704, Specific nitrogen 4.39, hardness5|. It becomescrystalline when heated t hour in The r- .f gbO"C (mean index of refraction 1-.76,specific gravity 4.55). these ray powder data are given in Table 3' It is not known whether data,refer to the original phase or to, one dr several recry'btallization products. The data dJnot correspondto any known yttrium mineral' of Sufficient material is lacking for'a chemical analysis' The presenoe lrp F in large amounts was confirted, and this eiement probably makes loss the bulf, of the shortage in Hidden's analysis. The small ignition and J."*"a presumably is"H2O, usually present in metamict minerals, SPENCITE AND ROWLANDITE 58] may represent essential (oH) in part. using an Jr-ray spectrograph with a LiF crystal and He path, borax fusions of the minerar werJ compared with borax standards containing known amounts of rare earths (together with Fe and si in the same amount as in rowlandite). The large ygo, content was confirmed.Determinations of the minor constituentsgave Ce and Nd in the range L to b per cent, with La, Mn, Th, U, Er, Lu, Dy, Ho, Gd, and Pr in amounts less than L per cent. An earlier optical spectrographicdetermination by K. E. valentine of the u.S. Geological survey gave Y and Si as the only major constituents with ce and Nd as minor constituents. Boron and Be are present only in traces, and p is lacking. The formula of the mineral is conjecturai .on the basis of.the existing analytical data. It may be near (y, Fe, Ca,.Ce, etc.)r(SiOrr(f., O{) crystalline phase ycO, I!". obtained by heating with S-iO,ir, ,h" ratio 1:2 in air at L000oC is neither identical,wifi rowlandite nor iso_ structural with SczSirOz(thortveitite) synthesizedsimilarly from Sc2O3 and Sior. A few grains of an altering reddish brown 'an )cc-raymineral were ob- served veining the rowlandite. These gave pattern closely resembling bastnaesite, but the mineral contains y much in excessof bastnaesitg !1.I.tlormal .was'identified in other specimensfrom Baringer Hill hereexamined. Rowlandite was named by Hidden after ihe. American physicist and spectrographer Henry A. Rowland (1g4g-1g01), of Joir". Hopkins who worked e{t t:":e""t1a of the rare earths.

,u":*:"tr"' 't. . RnpgnpNcEs. . Bn*11n1n1ncnn, (1940): parker E. cited in R. L. and-F.'de euervain: Gadolinit aus o"n pet. :"1*9y:I?tpen, Schweiz.Mi.n. Mitth., 20, I 1_l 6, 1940. CERIST,C. L. (1959): Garrelsiteand the datolite strucquregroup, Ame\. r77. Mi,n.,44, LZ6_ Fnovoer,, (1947): palache, C. Cited in Bermari and Frondel, Dana,s Syslem of Miner_ alogy,2,363,1951, (1957): Gev, P. An r'ray investigation of some rare-earth silicates: cerite, lessingite, beckelite, britholite, and stillwellite , M,in. Mag., gl, 4EE, Hess, (1908): F. L. Minerars of the rare-earth me[ab ai Baringer Hill, Llano cougly, Texas, [/.S. Geol,. Suro. Bul,l,., 340, 296-294. HroorN, w. E. (1891): Preliminary notice of a new yttrium silicare,Amer. J. sci.,42, 430. T., lJo, &-Monr, fI. (1953): lfhg crystal structure of datolite, Acta Cryst., 6, 2+-82. KnAMrn, H, & Ar.r-ox, (1956): R D. A restudy of bakeritl, il;i6 ;J'veatchite, Am. Min.,4f, 689-200. LAwnos, K. K. (1932): The Baringer Hill, Texas,pegmatite, Amer, Min.,17, gg1_gg0.. MrrTow,^C., Ax_rlnoo, J. M:, & G_nruar.or,f.. S. (fSbS): New mineral, garreisite,from the Green River formation, Utah, Bul,l,.Geol,. Soc. Amer., 66, LSSZ: PAvLov_, !. V., & Bor,ov.,-N. V. (lgb7): Crystal structure of herderite, datolite and _ gadolinite, Doklad.y Akad. Nauk S.S.S.R., 114, 884_gg7. SrRUNz,H. (1936): Datolith und Herderit, Zeits. Kryst.,93, 146_1b0. TENrvsoN, C. (1956): Cited by H. Strunz: Mineratog. TanLU,en,2nded., p. zZO, l}bl.