KAWAZULITE Bi,Te,,Se, RELATED BISMUTH MINERALS AND

Canadian Mineralogist Vol. 19,pp.34l-348 (1981)

KAWAZULITEBi,Te,,Se, RELATED BISMUTH MINERALS AND SELENIANCOVELLITE FROMTHE NORTHWESTTERRITORIES

RICHARD MILLER Departmentol Geology,University ol Alberta,Edmonton, Alberta T6G 2E3

Ansrnecr chalcopyriteassoci6s ont des propri6tdsoptiques et des compositionsnormales. Kawazulite. tellurobismuthite and selenian DIaz- (Fraduit par bleibend covellite are associated with Ditchblende la R6daction) and hematite in a breccia pipe that cuts Aphebian Mot.s-clis;kawazulite. tellurobismuthite. guanaiua- dacitic ignimbrites at Mazenod Lake. Northwesr tite, covelline,Se, Te, tsi, lac Mazenod,province Territories. Electron-microprobe analvses of kawa- de I'Ours, Territoires du Nord-Ouest.duret6. 16- zulite give Bi2.,sTe1.s6Se1.6and Bir.,rTez.nrSeo.oo,with flectivit6.microsonde. minor Cu and Fe. Three unidentified bismuth minerals (1, B, C'), with the general formula Bi,(S, Se,Te)r, were also found. Anisotropy for kawa- INrnoouctloN zulite is distinct, with polarization colors bluish grey to brownish grey; its measured reflectivity is A small U-Cu deposit occurs at Mazenod 60.0 to 6l.6Vo (547-591 nm). Telh.rrobismuthite Lake, Northwest Territories, on the so-called and mineral A have measured reflectivities of 61.5 Dianne mineral claims of the Noranda Explora- to 62.070 and 51.1 to 5l.6Vo. and micro-indentation tion Company Limited (Long. ll6"55TV, Lat. hardnessvalues (ZIlNm) of 155 to 180 and 199 to 63o45'30"N). A breccia pipe several hundred 205, respectively. This is not only the first reported metresin diameter,defined by tourmalinevein- Canadian occurrence. but also the recorded first lets and a large aeromagneticanomaly, cuts occurr€nce of kawazulite outside Japan. The covel- Iite, which exhibits weak anisotropy. contains up dacitic ignimbrites of the Great Bear plutonic- to 15 wt. 7o Se. Associated digenite and chalco- volcanic suite. These intensely hematized host pyrite have normal compositions and optical prop- rocks are occasionally cut by small ( 1 to 2 mm erties. across) veinlets of hematite-pitchblende that also host the Bi{u-Pb-$-Se-Te mineralization. Keywords; kawazulite. tellurobismuthite. guanaiua- Primary and secondaryhematite tite, covellite, Se, Te, Bi, Mazenod Lake. Bear can be distin- Province, Northwest Territories. hardness. re- guished in the veinlets; primary hematite has a flectivity. microprobe. platy habit, whereas secondary hematite, pro- duced by the oxidation of magnetite,is present Sorulrernr, as equidimensionalgrains with relict magnetite cores. The pipe exhibits extensive superficial Kawazulite, tellurobismuthite et covelline blau- copper-rich oxidation products. bleibend s6l6nifdre sont associ6es e la Ditchblende qui et ir I'h6matite dans une briche en Dipe re- MptttopoLocy coupe des ignimbrites dacitiques d'iee Aph6bien au lac Mazenod (Territoires du Nord-Ouest). La kawa- Reflectivity measurementswere made with a zulite possddela composition Bir.rJil.soser.or€t B2.,, photometer Te2.61Sen.eeavec un peu de Cu et de Fe (d6termina- calibrated to a tungsten carbide tions par microsonde 6lectronique). Trois min6raux standard (Carl Zeissno. 47 42 53). Reflectivity de bismuth. non-identifi6s (A, B et C): de formule is 46.1Vo aI 546 nm and 45.7Vo at 589 nm, id6alis6eBir(S, Se,Te)3, sont aussipr6sents. La kawa- with an accuracy of I I .5Vo. Monochromatic zulite est grise, anisotrope de bleuitre i bru- filters were used to obtain the wavelengths re- nAtre entre nicols crois6s. On mesure une r6flec- quired. The reflectivity values given are the tivit6 de 60.0 it 6l.6Vo (de 547 !r 591 nm). Pour highest of four or more measurements.Freshly la tellurobismuthite et l'espdce l, la r6flectivit6 n polished material was always used, since mineral les valeurs 61.6-62.OVo et 5l.l-5l.6Vo et la duret6 A and tellurobismuthite both showed significant (par miqo-indentation, VHNon). 155-180 et 199- 205. respectivement. C'est la premi€re fois qu'on brown tarnishing after a period of a month. trouve la kawazulite ailleurs qu'au Japon. La coveL Micro-indentation hardness was measured Iine, I6gBrement anisorope. contient iusqu'ir 157o with a Vickers diamond indenter. T\e VHN de Se (en poids). Les cristaux de die6nite et de numbers so obtained have been corrected bv 341 342 reference to a calibration curve, constructed by Bi. A comparison with the analysis of digenite comparing the measured and actual hardnesses suggeststhat this representsabout O.057o S, al- of a range of six standard minerals. This led to though its different atomic weight makes direct a corrected value about l1Vo lower than the ap- comparison uncertain. I suggestthat a detection parent value at VHNI : 100. Iimit of O.lVo is reasonablefor S in a matrix The electron-microprobe analyses all involve of SMOVo Bi, with an analytical accuracy of the energy-dispersiontechnique and were made -+ 0.2 wt. 7o. Similar logic gives slightly higher on an ARL EMX instrument fitted with an values for Pb in a Bi- or $rich matrix. Se, Te, ORTEC energy-dispersion analyzer. The data Fe and Cu are not subject to interference in were processedby the program EDATA2 (Smith this suite, and a detection limit of perhapsO.OSVo & Gold 1979). Count times were 400 seconds with an accuracy of * O.lVo is reasonable.The for both the standards and the samples, with situation for S deteriorates further in the Pb- full-spectrum total counts of 1.5 to 2.5 million. bearing phase, mineral A. The analytical X-ray The acceleratingvoltage was 15 kV in all cases. lines were Kcr for S, Fe and Cu;' La for Se, Ag Two sets of standards were used on differenr and Te; Mp for Pb and Bi. runs. One set comprised silver-bismuth selenide, coball telluride, chalcopyrite, pitchblende and MlNrletocv lead-silica glass. The second set comprised a gold-silver alloy, Bi, Se and Te metals, chal- The bismuth minerals found in this study all copyrite, pitchblende and lead-silica glass. As have the general formula Big(S,Se,Te)gand and Sb might be expected to be present, but a similar optical prop€rties. They were identified check by wavelength-dispersiontechniques did during routine electron-microprobe studies and not reveal them. cannot be distinguished optically except by re- EDATA2 calculates the background continu- flectivity measurements. Kawazulite was first um radiation for the average atomic number of reported and describedby Kato (1970), whose the specimen; experience to date confirms that type material came from the Kawazu mine, this procedure is entirely satisfactory (Smith & Japan. It has not apparently been reported in Gold 1979). Computer plots of the spectraafter the literature since then. removal of the calculated background showed The Canadian kawazulite occurs in trace no significant residuals.The background calcula- amounts, intimately associated with selenian tion is based upon a "normative background", covellite. The anhedral grains do not exceed derived from a diamond sample, which models 25 micrometres in diameter, so that X-ray-dif- precisely the efficiency characteristics of the fraction analysesand micro-indentation-hardness particular detector. measurements are not practicable. Trace The program is set to reject concentrations amounts of a similar phase occur nearby and of less than O.O3Voas being below detection form a very fine intergrowth with pitchblende limits. In practice, elements analyzed on high- and primary hematite. These grains are of the energy lines (i.e., 5 kV and up) under these order of one micrometre in size and may be a conditions have lower detection limits than this. different bismuth mineral. Kawazulite is also In the suite of elements sought, major overlaps found as myrmekitic, submicrometre inclusions occur htween the spectra of S, Pb and Bi, within the covellite; it has either exsolved from ranging from 26 to - lO0Vo. Overlap coeffi- covellite or coprecipitated with it. cients were calculated from the standards; the Tellurobismuthite has coprecipitated with close approach to 100% totals (with the ex- aboit SOVo pitchblende and is associatedwith ception of analyses 7-9) indicates that these some primary hematite. It is anhedral, forming coefficients are correct. However. the detect- grains generally less than 20 pm in diameter. ability of these elements is no longer of the It is also found as interstitial blebs, up to 100 order of O.O3Vo.For example, analysis l, on pm in diameter, between grains of secondary tellurobismuthite, had 301,134 counts in the hematite. There are trace amounts of chalcopy- Bi MB region of analysis.Of these counts,26Vo, rite, bornite and, rarely, covellite, but these are or 78,294, fall in the S region of analysis. The not closely associatedwith the tellurobismuthite. statistical varialion of these counts, i.e., the Mineral I was found in one veinlet as blebs square root (at the 1 a level), is 28O counts. up to l(D pm or more in diameter, interstitial At the 2.58 a or 99Vo confidence level, a peak to primary hematite. Although these blebs are of.722 counts could therefore register in the S large enough for microprobe analysis, they region, owing to Bi, which sets the limit on S nearly all contain exsolved rods of covellite, up detectability in the presence of this amount of to 10 pm long and 0.3 fr.- in diameter. Oc- KAWAZULITE FROM THE NORTHWEST TERRITORIES 343

Flc. -1..A. Mineral I (while) and minor covellite (mediunt grey) in hematite (lighr grey) and silicate (black): x8 objective, photographed under oil immersion (as B, C and D). B. Cential-grain of mineral I in Figure lA, x40 objective; exsolution rods of covellite are barely resolved at left, and three exsolution lamellae of mineral B (white) are at top. C. Left-hand section of grain of mineral I in Figure 18, xl00 objective; exsolution rods of covellite, in long and cross sections. D. Covellite grain, sarne scale as Figure lC, 100 rr,m from the grain of mineral l, shows myrmekitic exsolution of mineral l. casionally, the reverse relationship can also be Burke l97l). Figure I illustratesthe distribution seen. Like the kawazulite, mineral ,4 was pre- of this phase. cipitated simultaneously with covellite, and the Mineral B occurs as a few exsolution blebs in exsolution that resulted indicates a high-tem- mineral l. These blebs are about 2 x 10 pm perature solid solution between covellite and on average and have a rather higher reflectivity Biz(Se,Te)g. It is possible that this covellite is than the host. the selenian analogue, klockmannite, which has Mineral C occurs as a few single grains up to similar optical properties (Uytenbogaardt & 4 pm in diameter, intergrown with pitchblende 344 THE CANADIAN MINERALOGIST or primary hematite. The veinlet in which it The first of these minerals to be deposited was found adjoins the one containing kawazulite. at Mazenod Lake was magnetite, although noth- The selenian blaubleibend covellite commonly ing indicates the stage at which it was subse- primary hematite fol- occurs as grains up to l0O F,m across; it is a quently oxidized. Some primary mineral. A little secondary covellite lowed, before the main period of hematite forms alteration rims around chalcopyrite and formation and U-Cu-Bi-Pb-S-Se-Te mineral- bornite, which both occur as much smaller ization. Isotopic analysesby the author give an -+ grains. Chalcopyrite exsolution lamellae occur age of 4@ 3O Ma for the veins. A general within the bornite, which was not analyzed. age of 1800'Ma is assignedto the igneous rocks Digenite was identified optically, but Goble & of the Great Bear batholith. Smith (1973) studied very similar material and concluded that it was perhaps anilite that had Rrsurrs been converted to a digenite-like material by the Kawazulite polishing process; the same may also be true in this case. Analyses2 and 3 (Tables 1,2) areessentially

TABLEI. COMPOSITIONOF BISMUITIMINEMLS

BI Cu Pb Fe Ag s Se Te Totalr lllnera] 'r)52.6 (r{D) (ND) 0.45 (ND) (ilD) 0.26 46.3 99.95 Tellurcblsruthlte (thls study) 56.4 1.38 (ND)0.48 (ilD) (ND) 10.4 31.8 100.99 Kawazullte(thls studv) 56.3 (ND) (ND) 0.37 (ND) (ND) 9.92 32.4 99.33 Kawazullte(thls study) 31 '| (ND) (ND) t'tlneralA (thls studv) 48.8 6.35 't0.410.7 .02 32.9 O.9O l0l'08 1l 46.7 6.40 0.90 o.lo ([D) 33.6 0.79 99.19 Mlneral A (thls studv) 47.1 6.1410.2 2,01 0.23 (ilD) 33.5 0.93 I00.34 Hlneral A (thls studv) it 56.2 0.30 (ND) 2.24 (il0) ([D) 20.1 17.6 96.57 lllneral B (thls studv) (ND) 0.37 ([D) 1.47 l8.S 17.4 96.26 l'llneral B (thls studJ) ue) 55.1 n(o (llD) (t{D) (No) 14.6 25.1 97.25 tllneral c (thls stud.v)

comDositionsare expressedin weiqht %; ND: not detected. * Minor deviations from Ilsted totals are due to minor Si (less ahan0.2%) or U (less than 0.4%). The first maybe due to an error in backgroundfitting, the second to a halo effect from surrounding pitchblende.

TABLE2. COMP0SIT10N0F Bi2(S,Se,Te)3 MINERALS

Bl Cu fe Ag I Te lllnera'l (thls l) 2.06 (ND (ND) 0.07 (ND) (ND) 0.03't 2.97'l Tellumblsrnuthlte study) 2) 2.'130.17 (ND)0.07 (ND) (ND) .04 .96 Kawazullte(thls study) ?\ 2.r3 (ND)(ND) U.UJ (No1(ND) 0.99 2.01 Kawazullte(thls study)study, (ND) (ND) A (thls study) 4) 't1.65 0.710.37 0.l3 2.95 0.05 Mlneral .55 0.70 0.35 0.1I 0.0'l (ND) 2.96 0.04 filJnera'lA (thls study) 'l (thls 6) .56 0.67 0.34 0,25 0.02 (ND) 2.95 't.060.05 lllnera'l A study) 7) 2.06 0.04 (No; 0.31 (ND) (ND) 1.94 Hinera'lB (thls study) 'l 'l (thls 8) .80 0.62 (ND)0.05 (ND) 0.33 .70 0.97'l l.llneralB study) o\ 2.07 0.09 (ND)0.23 (ND) (ND) I .45 .55 lilineral C (thls study) l0) 2.18* - 3.00 -r|" B'lsnuthlnlie(DurembLruov6 & Kratochyfl'1977) l'l) 2.22# - 0.'10 . I .30 - 1.70 Tetradymlte(Durenrbergivi & Kratochvfl1977) t t? (Tlmofeevskll1972) '13)12) 1.73 0.05 tr 1.86 TetradhJte l.rt o:ou 1.04 tr 1.95 Tetradyrnlte(Tlrofeevskl I I 972) l4) 1,82 1.140.22 1.64 Tetradimite (Guha& Darling]972) '15) 1.260.48 1.27 Tetradyrnlte(Guha & Darllng 1972) 't6) 't.40 (Sarkar & Deb 1969) '17) 2.17 1.140.46 Tetradyrnlte . 2.03 1.00 - 2.O0 TetradymJte(Kashkal et al. 1974) (Harada '1972) 18) 2.30 (ND) lnol tHol 1.10(ND) r.eo Tetradvillte et al. '1944, 'l 'l (Palache p.162 anal.vsis8) le) .88 0.93 0.l8 'l .89 Tetradinlte et a]. nnl - .84 Tetradymite (Pllmr 1977) 20) 'l1.79 1.16 21) .60 0.40 l.ol - 1.38 plumulintetiadynlte (P'limer1977) 22) 1.92ll0.02 0.01 0.12 2.98 0.02 (ND) BJsmuthlnite (Harada et al. 1972) 23) 2.00 2.40 0.60 . - Bismuthlnlte(Prlache et al. 1944' p.276analysls 7) 24]- I .96 0.05 - 0.02 2.96 - 0.04 Blsmuthlnlte(Palache et al,1944, p.275 analysls4) 25) 2.01 0.t8 - 2.8? feiturouismuttilte(Palache et a1. 1944,p.160 analysls 4) 26) 2.0'l :: 0.03 0.02 2.94 Telluroblsmuthlte(Palache et al. 1944' p.'150analvsls 6) 271 I .83 n t7 2.47 - nq? Plumblancslklovalte (Pliner'1977) ,4, 2.05 0.t4 2,86 Guanajuatlte(Palache et a]. 1944,p.278 analvsls 2) (Pa'lache p.278 analysJs4) 2e) t.6v 1.21I .79 Guanaiuatlte et al. 1944, - # Thesevalues are (Bi+Sb Atomic proportions, S+Se+Te= 3. NDnot detected, no data. KA\VAZUI.,ITE FROM THE NORTHWEST TERRITORIES 345

identical, except for a little Cu in the former. BisCurPbrSere,with minor Te substituting for This may be due to copper in the kawazulite Se. Alternatively, the mineral may have a para- lattice rather than to exsolved covellite. since guanajuatite structure, presumed to be analogous sulfur was not detected. If the exsolution prod- to the tetradymite and tellurobismuthite struc- uct is klockmannite rathef than covellite, how- tures (Harker 1934, Brown & Lewis 1962), in ever, this could produce copper contamination which Bi has been replacedby 0.75(Pb*2Cu). without sulfur. However, these structures comprise hexagonal The optical properties of the kawazulite are: layers of close-packed,identical atoms in a five- reflectivity : 6O.OVoat 547 nm and 6l,6Vo at layer sandwich; for paraguanajuatitethis is (Se- 591 nm [cf., type material: 45 to 50Vo (Kato Bi-Se-Bi-Se), with metallic bonding within l97O)l; color white; bireflectance,twinning and layers and van der Waals bolds between ad- internal reflections not observed; anisotropy jacent Se layers. There is no space in the struc- strong, with colors bluish grey to brownish ture for the extra atoms required for the sug- grey (cf., type material: grey to reddish brown- gested substitution, unless voids are created in grey); VHN not obtainable, but the material the Se layers or unless Bi, Cu or Pb can sub- is markedly softer than covellite; one good cleav- stitute for Se. age locally visible. Brown & Lewis (1962) have shown that a The reflectivity and reddish anisotropy re- high degree of solid solution can occur in the ported for type kawazulite (Kato 1970) are Bi-Te system. The extra atoms are probably consistentwith a poor-quality polish, reducing accommodated by the addition of extra layers the reflectivity and giving false anisotropy colon. to the structure, such as those shown by Strunz Although X-ray-diffraction data exist for syn- ( | 963) in the system Bi-Se. Until more thetic BizTezSe(PDF 29-247), it has not been data are obtained, this mineral should perhaps possible to confirm that the mineral from Maz- be regarded as a Cu-Pb-bearing variety ofgua- enod [,ake is structurally identical to kawazu- najuatite or paraguanajuatite."Mineral S" (Cech lite. However, the electron-microprobeanalyses, & Vavlin 1978), PbCuBi(S,Se,Te)',is the clos- coupled with the generally strong physical re- est published analogue found by the author. It semblanceto the other minerals of the group, has the same property of being derivable from support the identification. a Biz(S,Se,Te),formula by the substitution of Pb*Cu for Bi, so that ionic chargeswould be Tellurobismuthite balanced. The measured. reflectivity of mineral u4 is The tellurobismuthite(analysis l) is interest- 51.1% at 547 nm and 5l.6Voat 591 nm; VHN:,, ing only becauseof the absenceof Se from the : 199l,O5. analysis, despite the Se-bearing minerals else- where. This suggests that there is no solid Mineral B solution between tellurobismuthite and kawazulite. Analyses7 and 8 (Tables 1,2'1 are less reli- The measured reflectivity .of the tellurobis- able than others in Table I becausemineral B, nruthite is 6l .6Vo at 547 nm and 62.OVoat 591 which exists as exsolved patches in mineral l. nm, both marginally below previously reported is too small to avoid significant contamination values; VHNro - 155-180, compared with re- during analysisby radiation from mineral I as ported valtres of ZllNrn - 32-93 (Uyten- well as from adjacent hematite (analysis 7) 'bogaardt ", & Burke l97l). and covellite (analysis 8). These patches or lamellae were also visibly affected by the elec- Mineral A tron beam: they turned brown. The other bis- n'luth phaseswere not markedly affected. Analyses4, 5 and 6 (Tables l, 2) are es- Both analysesof mineral B give low totals sentially identical. The grains commonly have (96.6 and 96.3Vo). A gtain was checkedquali- exsolved covellite (or klockmannite) rods in tatively by wavelength-dispersion methods to them: although visually clear areas were se- look for As or Sb, which could be hidden by lected for analysis, similar rods may have been the Se and Te X-ray peaks, respectively; none present below the sample surface but within the was found. The low analyses could be due to analyzed volume. However, the consistent Cu oxidation of the mineral surface during analysis and Pb contents suggestthat both of these ele- or to slight volatilization and crater formation n'rentsare contained within the mineral lattice. under the beam. Mineral B is a relatively The best-fitting fornrula from the analysesis minor product of exsolution;it possiblyhas the 346 THE CANADIAN MINERALOGIST formula BizSezTe,which would make it a previ- analyzed suites of anilite and blaubleibend ously unrecorded member of this mineral group. covellite and concluded that there are two varieties of the covellite, with the formulae Mineral C Cur.tu*o.orSand Cur.gz*o.uS[yarrowite and spionkopite, respectively, of Goble ( 1980)1. The Analysis 9 (Tables 1, 2) representsthe com- present study duplicates the yarrowite data, position BiaSegTea,a previously unrecorded with the formula Cut.p+o.or(S,Se).The digenite- species.As the grain analyzed is'small, confir- like altered anilite of Goble & Smith (1973) mation of the composition would be desirable. gave an average composition of Cur.re+o.ooS;the It may be a member of a solid solution whose digenite of this study may well be similar, with observed Se:Te ratio of 1:1 is a matter of the compositionCut.ra(S,Se). coincidence, but this ratio also suggests an The covellite is notable for its subdued bire- ordered phase. If we fit the formula to Harker's flectanceowhereas its anisotropy under crossed ( 1934) structural model as discussed,the logical nicols is much reduced. or even absent in a possibilities are that each Te or S layer of number of grains. Under oil, it remainsblue in Harker is filled with an ordered mixture of Se unpolarized or plane-polarized light. The ad- and Te, or that there are alternating layers of jacent digenite. bornite and chalcopyrite have (Te--Bi-Se-Bi-Te) and (Se-Bi-Te-Bi-Se), or normal optical properties. that there are alternating five-layer sandwiches of BLSesand BirTes. DIscussIoN

Selenian covellite Solid solutionis known to existin the seriesBi. S,rBirTer and BirSr-Bi^Se.,despite the different Selenian blaubleibend covellite occurs closely crystal structrlres involved in the latter series, associated with the bismuth minerals and as Named minerals in these series are bismuthinite exsolution bodies within them. There is evident- BisSs, orthorhombic; csiklovaite BLSrTe. "un- ly a solid solution between covellite and Bi: determined" (Roberts et al. 1974); tetradymite (Se,Te)s. As discussed,some of the smaller Bi,Te^S.rhombohedral (Harker 1934)l telluro- exsolution bodies may in fact be klockmannite, bismuthite BirTes" hexagonal or rhombohedral but are far too small to analyze. It is notable (Kato 1970); guanajuatite/paraguanajuatiteBi, that the digenite has comparatively little Se. Se" (Palache et al. l9M), orthorhombic/hex- and that the chalcopyrite has no detectable Se agonal [but note that Strunz (1963) gave para- at all. Te is probably incapable of entering these guanajuatiteas Bir(Se,S)s;Henley et al. (1975) lattices by virtue of its greater ionic size. gave guanajuatite as BigSe6; Roberts er a/. Ramdohr ( 1969) has attributed the blau- (1974) and othersgave Bir(Se,S)sfor both)l; bleibend effect to solid solution with CurS. which kawazulite BLTe'Se, rhombohedral (Bland & is borne out by the excessCu in the structural Basinski 196l). Bland & Basinski showed that formulae (Tables3, 4). Goble & Smith (1913) synthetic Bi"TezSeis isostructural with tetra: dymite, whose strtlcture was determined by Harker (1934). rAELE3. CO}IPOSITIONOF SETENIN COVEttITE Although solid solutions occur between the Cu Fe Pb S Se fe Tota'lr illnenl 30) S and Se"and S and Te end-members(Fig. 2), sr) apparently no analyseshave been reported along a' the Se-Te tieline apart from kawazulite. This iii study suggeststhe existence of two other min- line, BirSerTe(mineral B) and Expressedin reight g. * lllnor devlatlons from the listed totdls are due to erals along this traces of Sl (less than 0.29) or U (l€ss than 0.4r). The flht @y be due to (mineral five bismuth min- an error in backgrcund fltt'lng, the second my be a halo effct frcn adja- BirSerTer C). Of the cent Dltchblende. erals found in this study, tellurobismuthite was found in one veinlet, kawazuliteand mineral C TABLE4. COMPOSITIONOF SEIENIAN COVETLITE coexist in a second,and mineral A and exsolved mineral B occur in a third. This suggeststhat Cu Fe Pb Sse Te Mlneml 'I kawazulite 30) .05 0.02 tr 0.87 0.13 tr covelllte (thls study) there is no solid solution between 3l) I .05 0.07 0.01 0,77 0.23 tr Covel'llte (thls study) and mineral C, nor between mineral B and min- 1rl 1.19 0.09 0.02 0.80 0.20 tf Covelllte (thls study) I .11 0.04 0.01 0.80 0.20 (llD) covelllte (thls study) eral A (possibly guanajuatite). It is also likely 3;i 1.14 0.06 0.01 0.8t 0.19 (ND) Covelllte (thls study) is no solid solution between telluro- 1.73 'I0,03 0.01 0.94 0.06 (ND) Dlsenlte (thls study) that there fi' 0.97 .05 0.0.l 2.oo (ND) (ND) chalcopyrlte (thls studv) bismuthite and kawazulite, nor between mineral Expressedln atonJc proportions, SrSerTe" l. B and mineral C. Although these pairs were KAWAZULITE FROM TI{E NORTHWEST TERRITORIES 347

Bigadridu

Gillowite

Grmiuolib

]irftrotinnhib Bl2Te3 B.&r

Frc. 2. Reported analyses of Bir(S,Se,Te)g minerals; for key to individual analyses, see Table 2. not found coexisting, the common origin and Rerenrncrs proximity of the veinlets, coupled with the al- most perfect ratios of Se to Te, suppoft this Br-eNo, J.A. & BestNsrr, S.J. (1961): The crystal view. structure of BizTqSe. Can. J, Phys.39, 1040-1043. Despite the presence of sulfur in the veinlets. BnowN, A. & Lrwls, B. (1962): The systemsbis- as shown by the copper sulfides, there is virtually muth-tellurium and antimony-tellurium and the no sulfur in the bismuth minerals. This does synthesis of the minerals hedleyite and wehrlite. not necessarily indicate a miscibility gap be- J. Phys. Chent. Solids 23, 1597-t6O4. tween minerals along the BirTes-BizSeatieline (1978): PbBiz(Se, and BiaSa, but rather that chalcopyrite and Eror, r'. & Vavi,fx, I. Poubaite, Tg,S)n, a new mineral. Neues Jahrb. Mineral. digenite are intolerant of Se, whereas coVellite Monatsh.,9-19. is more tolerant and the bismuth minerals are more tolerant still. Under conditions of higher DuREMBERcov,(,D. & Knerocuvfr, F, (1977): Bis- sulfur availability, sulfur may well enter the muth- and tellurium-[e4ring minerals from Smolo- lattice of kawazulite and the unidentified min- tely near ffibram. dasopis Mineral. Geol, 22, erals. 4O7-4lO (in Czech.; see also Mineral. Abstr. 29, 78-4909).

AcKNowLEDGEMENTs FANDER,H.W. ( 1967): Seleniumat Peko and Cobar. Aust. Mineral. Dev. Lab. (AMDEL'I Bull. 2. I extend particular thanks to Mr. S. I-aun- 73-75 (see also Mineral. Abstr. 18, 281). spach, microprobe operator at the University of R.J. (1980): Copper sulfidesfrom Alberta: Alberta. The microprobe facilities are supported Gonle, yarrowite CusSe and spionkopite CuggSre.Ccl. grant by NSERC A4254 to D.G.W. Smith. Mineral. 18, 51l-518. Optical work was made possible by NSERC grant A4242 to R.D. Morton. Noranda Explo- & Sutrn, D.G.W. (1973): Electron micro- ration Company Limited kindly allowed access probe investigation of copper sulphides in the to their property; field expenseswere met by Precambrian Lewis series of S.W. Alberta" Can- the Department of Indian Affairs and Northern ada. Can. Mineral 12, 95-103. Development, Yellowknife. The manuscript Guse, J. & DenuNc, R. (1912): Ore mineralogy benefited from critical reading by Roger Morton, of the Louvem copper deposit, Val D'Or, Que- Dorian Smith and anonymous referees. bec. Can. l. Earth Sci. 9. 1596-1611. 348 THE CANADIAN MINERALOGIST

(1977): Bismuth minerals from quartz HARADA,K., Necesnrue, K., Mtvorawe, K. & Yut' PLIMER,I.R. Ausffalia, Aust. Mineral' LO, S. (1972): Bismuthinite and cosalite from Age- pipes in eastern nosawa mine, Akita Prefecture, lapan. Geol. Soc' 4l-43. Japan 1.78, 485'488. RAMDoHR,P. (1969): The Ore Minerals and Their London. HARKER,D. (1934): The crystal structure of the I ntergrowths, Pergamon, Bi"Te2S. Z, Krist. 89, 175- mineral tetradymite, Ronrnrs, W.L., Rlpp, G.R. & Wrarn, J. ($74): 18l. Encyclopaedia of Minerals, Van Nostrand & York. HENr-sv, K.J., Scnulrz, P.K. & BnowN, R.N. Reinhold. New (1975): to Australian mineralogy. Contributions Srnrrn, S.C. & Des, M. (1969): Tetradymite and seleniferous bis- 7. The compositional range of wehriite from Singhbhum copper-belt, India. ore deposit, Ten- muth sulphosalts in the Juno Mineral. Mag. 87, 423-425. nant Creek. N.T. lusr. Mineral. Dev. Lab. (AMDEL) Bull. 20, 1-18 (see also Mineral. Srrarrn,D.G.W. & Gorp, C.M. (1979): EDATA2: Abstr. 27, 7C3U9), a Fortran lV computer program for processing wavelength. and/or energy-dispersive electron (1972): Twenty-seventh Hrv. M.H. & Eunnrv, P. microprobe analyses. In Microbeam Anal, Soc' Mag. t8, list of new mineral names. Mineral. Proc. I4th Ann. Conf . (San Antonio 1979; D.E.' 987-1001. Newbury, ed.), 273-278. -._- (1974): A second appendix to & SlnuNz, H. (1963): Homiiotypie Bi2Se5Bi2Ses-Bi.t of mineral species the second edition of an index Ser-BirSesusw. (Platynit, lkunolith' Laitakarit). Mus. and varieties arranged chemically. Brit. Neues Jahrb, Mineral. Monatsh., 154-157. (Nat. Hist.) Publ. 725. TrMoFEEvsKIf, D.A. (1972): Bismuth sulfotellurides A.A. KesHrat, M.A., Mlrxrrunov, A.I. & MAGRIBI, in the Darasun ore field, eastern Transbaikalia. (1974): Tetradymile and hessite from chalco- Zap, Vses, Mineral, Obshchest. 101, 24-35 (in de- pyrite and pyrite ores from the Kashkachai Russ.;see also Mineral. Abstr.23, 72-3330), posit in the Dashkesanregion of the.{zerbaidzhan SSR. Dotl. Akad. Nauk Azerb. S.S.R, 30, 62-66 UyrrNBocAenDT,W. & Bumr, E. (1971): Tables (in Russ.; see also M'neral. Abstr. 27, 76-844). for Microscopic ldentification of Ore Minerals. (2nd ed.). Elsevier, Amsterdam. Kero, A. (1970): ln Introduction to JapaneseMin- erals. Geol. Surv. Japan 1970, 87-88. Per,rcHr, C., Br.nueN, H. & FnoNpst, C. (1944'): Dana's System of Mineralogy. I. Elements, Sul- fides, Sulfosalts, Oxides. J. Wiley & Sons, New Received October /,980, revised nranuscript ac' York. cepled February 1981,