1301 Thz Carwd.ian M ineralo gist Vol. 36, pp. l30l-13M (1998) WILUITE,Gars(Al,Mg,Fe,Ti)13(B,Al,!)5Si1sO6s(O,OH)ro, A NEWMINERAL SPECIES ISOSTRUCTURALWITH VESUVIANITE, FROM THE SAKHA REPUBLIC, RUSSIANFEDERATION LEE A. GROATI Depamnent of Earth anl Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6R 124 FRANKC. TIAWTHORNE Departmcnt of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2 T. SCOTTERCIT andJOEL D. GRICE Mineral Sciences Division, Carudian Museum of Nanre, Onatva. Ontario KlP 6P4 AssrRAcr Wiluite, Cale(At,Mg,Fe,Ti)13(B,A1,E)5SirrOes(OH,F,O)ro,rerragonal, a 15.752(L),c ll.7l7(l) A, V ZgOl.Z(Z)A3, space grotpP4lnnc,Z = 2, is a newmineral species of thevesuvianils g'.up from theWilui River,SakhaRepublic, Russian Federation. Itoccunasholosymmsfficcrystalswithforms(100Jand{101}dominantplusrninor{110}and{001},upto3X3x5cm, slightly elongatealong [001]. f{6 fiTvinningwas observed. Wiluite is darkgreen with a colorlessstreal<, a vitreousluster, and it doesnot fluoresceunder long- or short-waveultraviolet lighr It hasa Mohs hardnessof 6, is brittle with an irregularfracture, and haspoor cleavageon { 100}.The measureddensity is 3.36(3)glcm3, and the calculateddensity is 3.358g/cm3. In transmitted light, vdluiteis colorlessand nonpleochroic; it is uniaxial-positivewith a = 1.721(2)and e = 1.725(2).The strongestten reflec- tions in the X-ray powder-diffractionpattern ld(in A)(I)(hkDl are2.'176(100)(342),2.617(61)(252),2.491(61)(260), 2.s92(43)(224),r.66(26)(346), r.640(23)(292),2.r21(20)(r3s),3.s2(r8)(240), 1.987(1sxs6r),2.929(14)(004), and 2.912(14)(233).An analysisof wiluite gaveSiO236.Ll, A12O312.03, TiO2 0.80, MgO 6.48,FeO l.21,Fezo32.28,CaO35.54, Ce2O30.18, BzO: 3.06,F 0.50,H2O 0.61, O = F 4,24, sum= 99.20wt.Va.Ttie concentrarion of FeOwas determined by wet chemistry,and that of H2Owas determinedwith a LECO induction furnace;the concentrationof the other elementswas deter- minsd fy electron-microprobeanalysis. The correspondingunit formula,based on 19(Ca+ Ce), is (Ca1s.97Ceo.o:)>rs (Al6r3TiffoFes6N4ga.s1Fe5s)p13(B2.63A1s.511.sa)z5Sirz.qsOoe[(OfDz.oso7.r]>ro. Wiluite is isostructuralwith vesuvianite,and con- tainsessential B [B > 2.5 apfu (xoms per formulaunit)]; vesuvianiteis uniaxial (-), wiluite is uniaxial(+). It occurswith grossularand serpentineminerals in a serpentinite.The namerecalls the localiry, and has beenin use as a varietal name for "vesuvianite"from this locality for over 200 years. Keywords:wiluite, new rnineralspecies, electron-microprobe analysis, X-ray powder-diffractiondat4 vesuvianite,boron min- era1,Yakutia. Russia- Sopnaene Nous d6crivonsla wiluite, Cale(Al,Mg"Fe,TDr3@,Al,E)sSilaOoe(OH,F,O)ro,t6tragonale, a 15.752(1),c ll.7I70) A, V 2907.3(3)A3, groupe spatial P4lnnc, Z= 2. commenoun"au membre du groupede la v6iuvianiteprovenant de la rivibreWilui, enR6publique de Sakh4 F6d6ration Russe. Elle sepr6sente en cristaux holosym6triques montrant les forrnes dominantes { 100} et {101},etenplus, {110J et {001}moinsimportantes;ils atteignentunetaillemaximumde3 x 3 x 5 cm,etsontl6gerement allong6ssur [001].Aucune macle n'a€t€ d6cel€e.La wiluite estvert fonc6avec utre ra]ure incoloreet un 6clatvireux. Elle ne montreaucune fluorescence en lumibreultra-violette, soit en ondeslongues ou courtes.Sa duret6 est de 6; elle estcassante, et fait preuved'une fracnue irr6gulibre et d'un pidfe clivagesur { 100}. La densit6mesur6e est de 3.36(3), et la densit6calculde, 3.358 g/cm3.En fumi|1g6an5mise, la wiluite est incoloreet non pl6ochroique;els s51uniaxe positive, avec o = 1.72I(2) et e = 1.725(2).Les dix raiesles plus intensesdu spectrede diffractionX td(enA)(IXrftDlsoat2.776(100)(342),2.617(61)(252), 2.49r(6r)(260),2.592(43)(224),1.66(26)(346),r.&O(23)(2e2),2.r2r(2o)(r3s),3.52(18)(240),1.987(rs)(s6r),2.929(r4)(0M), et2.9l2(14)Q33).Une analyse chimique de la wiluite a donn6SiOz36.lI, AlzOg12.03,'tiOz 0.80, MgO 6.48,FeO 1.21,FezO: ' E-mail address: [email protected] 1302 2.28,CaO35.54, Ce2O30.18, B2O33.06, F 0.50, HzO 0.61,O = F 4.24, pour un total de 99.20Vaparpoids. La concentration de FeO a 6€ d6termin6e par voie hnmide, et la teneur enHzo a eG 6tablie au moyen d'un four tr induction LECO. Le niveau de concenmdon des autres6l6ments a€t€Atabh,pat microsonde dlectronique.La formule chimique qui en resulte, fond6e sur 19(Ca + Ce), est (Ca16.e7Cee.e3)21e(,{16.53Tie.3eFes6Mga.8lFe50)>13(B2.63Ale.53n1.ea)>5silz.eeo6s[(OH)z.olOr.g7]>10.La wiluite est isostrucnrale avec la v6suvianite, et contient le bore comme constituent essentiel (>2.5 atomes de B par unit6 formulaire). La vdsuvianite est uniaxe (-), tandis que la wiluite est uniaxe (+). On trouve la wiluite avec le grossulaire et des min6raux du groupe de la serpentine.lans une serpentinite. Le nom rappelle la localit6, et sert ddja depuis plus de 200 ans pour signifier lavari€t6, de '!6suvianite" provenant de cet endroit. (Traduit par la R6daction) Mots-clCs: wil'uite, nouvelle espdcemin6rale, analysed la miqosonde 6lectronique,diffraction X sur poudre, v6suvianite, minfpl de bore, Yakoutie, Russie. INrnopucnom cal sector zoning; {001 } sectorsshows a cross-hatched pattern,possibly due to twinning, and the {110} and It has long beenknown (Jannasch1884, Widman { 100} sectorsshow fine striations.The {001 } sectorhas 1890,Jannasch & Weingarten1896) that vesuvianite a low birefringence and is slightly biaxial, withO <2V can containsignificant boron. Groat et al. (1992) < l0o; the { 100} sectorshave higher bireftingence, and showedthat vesuvianite samples from severallocalities 2V vaies within the range l0 < 2V < 25" . The to and e containhigh (>1 vrt.VoBzO) contentsof boron. Groat indices of refraction of the {001 } sector in monochro- et al. (1994) examinedthe mechanismwhereby boron matic light (590 nm) are 1.721(2) and 1.725(2),respec- is incorporatedinto vesuvianite,and showed that boron tively. The compatibility index is 0.008: superior. occupiestwo newly identifiedsites in the structure.If Boron-free and boron-poor vesuvianitesare uniaxial (or the occupancyof one or more of thesesites by boron slightly biaxial) negative. The composition (i.e., B con- becomesdemin2a1, then a newmineral species is estab- tent) at which the optic sign changesis not known, but lished.Vesuvianite from theWilui Riverhas long been the optic sign is a simple indicator of high-B vesuvianite known to have a high boron content,and the work of and wiluite. Groatet al. (1994)showed that vesuvianitefrom this localitycontains sufficient boron to establisha newspe- Cmvucer CowosrnoN cies.The new mineral is namedwiluite, a"fterthe local- ity, theWilui River,Sakha Republic (Yakutia), Russian Crystals were analyzedchemically with aJEOL733 Federation.The new mineral and mineralname have electron microprobe operating in wavelenglh-dispersion been approvedby the InternationalMineralogical As- mode with an acceleratingvoltage of 15 kV and a speci sociationCommission on New Mineralsand Mineral men current of 25 nA. Data on standards were collected Names.Type material is depositedat the Canadian to O.25Voprecision or for 25 seconds,whichever was Museumof Narure,Ottawa" Ontario, Canada. less. Data on each element were collected to 0.5Vopre- cision or for 50 seconds.The beam size was 10 or PHvsIcar Pnopnnrms 20 Um, and counting t;mes on peak and background, 20 and 10 s, respectively. The following standardswere Wiluite occursas isolated holosymmetric crystals up used: diopside (Si), almandine (Al,Mg,Fe), titanite (Ti), to 3 X 3 ( 5 cm (ll a, b, c, respectlely).The dominant tephroite (Mn), gehlenite (Ca), elbaite @), glass 5-254 formsare {100} and {101},with minor {110} and (Ce) and fluororiebeckite (F). The FeO content was de- {001}; no twinningwas observed. Wiluite is darkgreen termhed by tihation. The H2O content was determined with a colorlessstreak and a vitreouslusler; it doesnot with a LECO induction furnace. Data were reduced us- fluoresceunder longwave or shortwaveultraviolet light. ing conventional ZAF techniques. The mean of twenty- It is brittle with a poor cleavageon {100}, and as an five determinations is given in Table 1; the crystals are irregular fracture and a Mohs hardnessof 6. The den- chemically homogeneous. The chemical formula was sity wasmeasured with a Bermanbalance using toluene calculated on the basis of 19 X cations (= Ca + Ce), as at29"C;the measured density is 3.36(3)g/cm3, and the recommended by Groat et al. (1992); the resulting for- calculateddensity is 3.358g/cm3. mula is given in Table 1. A simplified formula may be written as Cale (Al,Mg,Fe,Ti)t, (B,Al,n)s Sire Oos Orncar Pnopsnrms (O,OH)1e. In transminedlight, wiluite is colorlessand non- Trn Lnrmrnc B Covrem oF WLUTTE pleochroic.Although morphologicallytetragonal, wiluite shows"anomalous" optical properties in cross- As shownby Groatet al. (1994,1996),8 occupies r/+] r/+1/+ r/+] polarizedlight (Groater al. 1993).There is strongopti- the Z(l) [ 0.055,0.055, atdT(2) [ sitesin WILUITE FROM YAKUTL!\. RUSSIA 1303 TABLE1. cHEMICALoOMPoSITION' (wt.%) diffractometry showed the crystal tohave lmmtnLate ANDUNI-I FORMULA (eptu) FOR WILUIE symmetry; furthermore, the extinction conditions are sioz 36.11 Si 17.99 compatible with P4lnnc space-grolp symmetry. Details Alro, '12.03 of the refined crystal-structure are given by Groat et al. lto, 0.8 (1994), and the polarized ffiared spectrum is given by Ir/gO 6.48 AI 0.53 Groat et aI. (1995). FeO 1.21 tr 1.U Fe.O. 2.28 OccuRnm,tce arvo Assoqnrsl MweRAI-s CaO 35.54 Ce2O. 0.18 AI 6.53 Wiluite occurs associated with grossular in a matrix BrO, 3.06 II 0.3 of fine-grained serpentine minerals, carbonate, Fe$ 0.86 limonitized pyrite, chlorite and "achtarandid', a teta- HrO 0.61 Fe2* NA pseudomorph of rrnknown precursor mineral O"F 4.24 lr/S 4.81 hedral an from the Wilui River region, Yakutia, Russia (Grew rotal T 994_ 1996), tentatively identified as wadalite (Galuskina et Ca 18.97 al.