A STUDYOF PYROCHLOREAND BETAFITE D. D. HOGARTH Unhsersityof Ottawo, Ottowa' Canad'a ASSIRACT several types canadian occur- Pvrochlore and betafrte were investigated from 9f eleven analyses for eight con- ,*iJ"""1it* ;;;G; f;t*;;ty ;nstituents and oH)18(F' oH)s is proposedfor stituenta are presented.2i;;;il;l*;lu-i*-"n'u(o' sites in the unit cell. Differen- the pyrochlore-betafite serie"switlr r representing vaLnt two states of water' Betafite and tial thermal and thermogravimetric curves indicate can begin w-ell the exo' thorian pyrochlore tt" t"l,i-i.i, id"i recrrs4li'ation .below edge of ignitea minerals tends to thermic reaction indicateiln b.r.n. ."*o. The cell *"ig-ttt" dirived from densitv-cell decrease as titanium i;;i;;;;;. Molec'lar ""i irom analyses. Observed r-ray edee data correspond q""fiilii""i' a. ii,o"e .al"ul"ted role of iron is uncertain. Frequency il1;#;;";;irh;d;;J;.iues, but the and betafite at 15 per cent uranium. dragrams suggesr u ,ru.ur;l*Jio-i;io" Jpyro"hloru Iutnoouctton long been disputed' The relationship of pyrochlore and betafite has betafite are very X-ray powder patterns of pyrochlore and ignited quite different. Pertinent ,i*if", tut chemical compositions are usually (1932), who showed chemical work has U""" i"ported by Machatschki flom stoichio- that membersof the;yro"hlo." seriesdepart considerably that vacant cationic ;"ary, and Ros6n &'W""tg'"" (1938), who showed structure' Borodin & sites are common it with the pyrochlore "o*pJt"ds structure occurs in Nazarenko (1957) mainiain that this type of defect the pyrochlore series natural pyrochlore. Ci.rf"tg et at' (1958) extended formula Az-,BzXz'The to include betafite rJ a3A-iite wiih the general last two publications writer's research*., n"utty complete before these substantiates becameavailable. A new .t"""s'ne"t of data independently the main conclusionsof the Russian authors' been known for some The symmetry and structure of pyrochl'orehave - Gaertner (1930); time. The spacegroup was determined as OI Fd'\mby (1941), using- morphological using rc-ray diffraction and by Donnay is describedas the type data. Gaertner also determined the structure. It -E8rin the Struhturberi,cht. a state which has All betafite and some pyrochlore are metamict' to take place with frindered ,-ruy irr',r"Jig"tit"' Crystallization is known The exothermic pheno- evolution of heat whei the minerals are ignited. curves (Kurath, mena are -.rrirot"J,s f"arc on differential thermal mineral do not always igfD. Peaks that are typical for th9 -specific appear (Kulp, Volchock, & Holland, 1952)' 610 Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/6/5/610/3458092/610.pdf by guest on 24 September 2021 P]TROCELORE AND BETAFITE 611 x-ray diffraction patterns of pyrochlore and ignited betafite are similar although not identical. A structural relatioriship between the two mineralswas proposedby Bilrlykke (1981)and Reuning (1988),but contested by Machatschki (1982). Rutile and pyrochlore lines were identified in the x-ray patterns of ignited betafite by Takubo, ueda, & Nishimura (1951).A uraninite structure may arsoappear as was shown by Gasperin(1957). Furthermore, Sfrum (195b)ignited metamicr pyro- chlore and obtained, besidespyrochlore, r-ray rinesof columbite, loparite, and a new phaseof uncertain composition. DnscnrptroNs oF Seupr,Bs ewn OccunRENcES Mineral, Separation samples of pyrochlore and betafite were separated in ottawa at the Geological survey of canada and at the Mines Branch, Department of Mines and rechnical surveys. Most sampleswere concentrated by hand under the binocularmicroscope but some(Hg-1-1, Hg-1-4, and H9-1-HS) were concentrated on the Frantz isodynamic separator, upgraded on the Haultain superpanner, and finally handpicked under the binocular microscope. sample H8A was passed through the Frantz isodynamic separator, and a heavy liquid concentrate (sink from diluted clerici solution) was made by Dr. E. H. Nickel of the Division of Mineral Dressing and ProcessMetallurgy, Mines Branch. Mineral association, purity, and zoning of pyrochrore and betafite grains were studied by means of thin sections, polished sections, and autoradiographs. Autoradiographs were taken on Kodak, ff-ray, no- screenfilm. Most sample concentrates weighed from 2 to b grams although five samples weighed about L gram and one sample (Hg4B) weighed only 0.3 gram. Lack of material limited the number and type of tests for many samples. sample data are listed in Table 1. Data are not included for samples Hlc and HZ which had been separated previously by Dr. R. J. Tiaill and were given to the writer in powder form. sampre Hrc is a rare thorian variety of pyrochlore from Blue River, British columbia, while H7 is the "betafite" from the Manny zone, Molybdenum corporation of America, Oka, Quebec(Rowe, lgbb, p. 5, ,,betafite"). Occurrence The geological occurrenceof most deposits from which samples were taken has been previously described and only a few generalizationswill be given in this paper. occurrencesare summarized and referenceslisted Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/6/5/610/3458092/610.pdf by guest on 24 September 2021 N io E oad 5 45..i:: g -j9966 .F h I 3 =:q'asg(,)<< o a + i ; a d d ! t 99c e q qmm ts 6 { ! i a i ; = s a<a f o 6; 6: o il a el v X o -PH:i H : X ;3E-E"E-B E n =- ) "i d 6 €t c : I i> c :+ N 5 CErq :t )B b9 i. 588 sF' t7 io i't :9 l9 3U a) # c 5 i ii€ E I o f ) B i^ $n"9 tr Q o l8S'i aF,g ar s d tq$..iP r ofl j N\x EA .:o o!s E r sn a; a E@id EEg d ?,nd NFO; E d A HM fr1 E o {c E ,? d F s I 5 ho r9 l4q@ (ac tE$! : Nt\ Ft- <dj'iJ' d Io o <i EA 9,4 ^+ h !6 o!s o1 .l q €t d xx o cJ .O q v €F Brg E EFE x q u >= t sj3HEE EI ul Ke B N! "B E s R3 4i{ o q u. 6 e qdq ol9 E !0 (n9\6 i dF A :tsts J,i ! 5! F .E u q! 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I /l dlc .9 I F gEEig€ *lz tq!i!e F=^= g I ; <??l {6 IX € I tHoi E i Fc *l; : I P t$b Hl O d I 3 .. J oN dIO * I :r { |E: *t3Hl - i I d Y l-tr s I : € ^ o-lrd tr | N 3ap$ F=r)<<l:n€EEi s? iE l9t I ulc. Eseu;E$gEs F I 3a "i E .sle5 € 8 tFEIF! EB 6ir .:XFl:i isEssEggsss;jce ^= d,?dlF"g I x loi ',b ^ .EE 1q n b'EH iITF€; ,bs r.E EF g;F ?g"e ".,s| i5g [i Ep q&"= rBs F8 IE t!a sE;$3E$31n5 Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/6/5/610/3458092/610.pdf by guest on 24 September 2021 614 THE CANADIAN MINERALOGIST Ph'D' thesis (Hogarth' in Table 1. Further details are given in the writer's 195e). British Columbia' and Well-crystallized pyrochlore at Blue River' rock' The Blue River pyrochlore is Oka, Quebec, o""rrr.'in carbonate appears to have been found in both aoto*it" and calcite' Dolomite At Oka pyrochlore was granulated. Pyrochlore often contains columbite' The larger grains contain observed in calcite- and diopside-rich rocks' pyrochlore both localities is frequently abundant gangue -i"Jr. from exterior of the crystal. zoned with the -ort,Jouctive zone at the The pegmatites Betafite was studied from several types of occurrence' Ontario' contain unzoned of Viking Uf.u, Su"'Lt"hu*t", and-Hybla' veins and ellipsoidal and usually u.rf,"arrif"iJt". detafite fiom calcite near Bancroft, Ontario' calcite bodiesof the Hofan and Basin occurrences ,,cubo-octahedral" in habit. Betafite in the is unzoned u,rt "o--ffi is octahedral and some- amphibole-ri.t, ,r"it"l,t--fi"ll to*""hip' Quebec' The associatedbreccias also times zonedwith a J;;i;;"Jioactive iim.