Canadian Mineralogist
Yol.22, pp. 487-491(1984)

JASKoLSKIITEFROMIZOKLAKE,NORTHWESTTERRITORIESDONALD C. I{ARRIS AND ANDREW C. ROBERTS
GeologicalSuney of Canada,601Booth Street,Ottawa,OntarioKIA 088
ALAN J. CRIDDLE
Departmentof Mineraloglt,British Museum(NaturalHistory), CromwellRoad,London, EnglandSW7sBD

Bi et x=0.15.

ABSTRACTA second ocourence of jaskdlskiite has been found in Mots-clds:jaskdlskiite,sulfoseldePb-Cu-Sb-Bi' lac Izok
(Ierritoires du Nord-Ouest),r€flectance,analysei lathe massivezinc-copper-lead sulfide deposit at Izok Lake,
Nortlwest Territories. The mineral occurs as lath-shaped
microsondedlectronique,clichdde poudre.
crystalsup to 150x 3@ pm.in galenaassociatedwith pyrite,pyrrhotite, marcasite,chalcopyrite, tetrahedrite and nativebismuttr. In reflected, plane-polarized light the mineral isINtnopuc"floN
strongly bteflectant from greenishgrey to greenishwhite,with no reflectancepleochroism. It is strongly anisotropic.
Jask6lskiite is a newly discovered Pb-Cu-Sb-Bi
I4tN5o 148-185. Reflectancespectra and color values forsulfosalt from the Vena deposit, Sweden,describedtlree grainsare zupplied.The structural cell is orthorhomb^icin this issueby Zakrzewski(1984).Simultaneously,with dimensions:a 11.31(l), b 19.79Q),c 4.087(4)A.
a secondoccurrenceof this mineral was discovered
Two space gxoups are possible: Pbnn al:.d Pbn21, !:heduring a sfudy of the Izok Lake massive sulfide
powderpatternstrongest six lines of the X-ray
td in A 0)
deposit, Northwest Territories. Polished sectionsof(h kt))u e: 2.75| (l 00X30I, 24l, 3I 1), 3.73(90X150,?4,3 l0),
2.9s7 (n)Q3r), 3.59(60)(121),3.33(60xl3l), 1.787(60) jask6lskiite from Izok Lake are depositedin the Na(312,0101). An electron-microprobe analysis of a single tional Mineral Reference Collection housed at thespecimengaveCu 0.8, Pb 48.5, Bi l7 .4, Sb 14.6, S 17.6, Geological Survey of Canada, Ottawa, the British
total 98.9 wt.Vo, which conesponds to the formula
Museum (Natural History), the Royal Ontario MusePb2+rculsb,Bi)z-Ss, with Sb > Bi, r=0.15.
um, Toronto and the Bureau de RecherchesG6olo-elques ef Minidres, Orl6ans, France.
Keywords: ja,sk6lskiite,Pb-Cu-Sb-Bi sulfosalt, Izok Lake,
Northwest Territories, reflectance data, microprobe
analysis, X-ray powder data.

OccumeNcs

Izok Lake is locatedat 65o39'N, 112o49'Win thenorthern part of the Slavestrucfural province, NorthSoNaN{ernewest Territories. It is 366 km north of Yellowknife
and 3@ km south-southeastof Coppermine,the twoOn signale la deuxibmelocalit6 de la jask6lskiite, dans nearestsettlements.The geolory and exploration hisle gite de sulfures massifsde Zn, Cu et Pb du lac Izok (Iertory of the deposit are given by Money & Heslop
ritoires du Nord-Ouest). Les cristaux, 91 minggs plaquet- (1976) and Bostock (1980). The deposit occurs intes qui atteingnenr 150x300 pm, se pr6sententdans La highly metamorphosedArchean metavolcanicrocks
galbne qui fait partie de I'assemblagepyrite, pyrrhotine,
have undergone at least three major phasesof
marcasite, chalcopyrite, t6tra6drite et bismuth natif. En thatfolding.
lumidre r6fl6chie polarisde rectilignement, cette especeest
The major ore-mineralsare pyrite, sphalerite,pyrfortement bir6flectante de gris verdfitre d blanc verd6tre.
Elle ne monlre aucun pl6ochroismede r6flectance,mais elle rhotite, silver-bearing chalcopyrite, magnetite andest fortement anisotrope. ZftNsg 148-185.On pr&ente des silver-bearing galena, with minor to trace amounts
spectresde rdflectanceet une €valuation de la couleur pour of thirty-one other species.A completemineralogitrois grains. La maillg est orthorhombique, a 11.31(1),b cal description of the Izok Lake deposit will be
19.79Q\, c 4.087(4)A. Le groupe spatial est Pbnm ot
reported elsewhere.Jask6lskiiteis rare in the deposit,Pbn21. Lgs six raies les plus intensesdu ctch6 de poudre having been identified in only 3 of the 38 drill holes
ld en A (l) (hkl)\ sont:2.751(100X301,241,311),examined.It is most abundant in drill hole 88, where
2.957(90X23l), 3.59(60X121),3.73(90X150,240,310),
it occurs in galena-rich stringer ore between 44.2to
3.33(60)(13l),1.787(60)(312,0101).Une analysei la
48.2m and between58.8to 60.4m. In drill hole l3,itCu
Pb
4.5,
Bi17.4,
microsondedlectroniquea donn6: 0.8,
Sb 14.6,S 17.6,total 98.9V0(en poids), ce qui correspond is lessabundant, occruring between58.8 to 59.7m
in disseminated galena within a chlorite-biotitei la formule Pb2*rCulSb,Bi)z-Ss, dans laquelle Sb >

487

488

TIIE CANADIAN MINERALOGISTTABLEI. COMPOSITION
OF JASKOLSKIITEFROMIZOK LAKE
I9eight percent
Sample

CuPb

Bi5b

Hole EE,lJ3.l
Hole 13, 193.0
Hole 8,222.0

AC0.E 0 . E 0.2
0.5 -HoleE8,1r3.lH o l e1 3 , 1 9 3 . 0
HoleE,222.0

Atomic proportiom
0.11 2.13 0.76 1.09
0.12 0.O22.12 0.77 l.$
0.0E 2.13 0,67 l.L25Tota.l

4E.5 17.4 r 4 . 6 17.6 98.9
49,4 18.0 1 4 . 1 18.0 100.,
49.3 15.7 L ) . 2 t7 .9 9E.7

555

Th@retical Formuls Pb?.. Cu" 6b, Bi)r_* 5, with
Sb > Bi. x about 0.15. "^Compositions ar€ derlved fron electron-mlcroprobe data.

cordierite footwall of the massiveore-zone.In drill
hole 8, it was identified in one polished section at67.7 m, occurring with native bismuth as inclusions
in galena. Sinceall Izok Lake drill-core lengthswere
recordedin feet, the sample-numberdesignationusedin the tables and figures refers to feet.
ELEcTRoN-MIcRoPRoBE
ANAr.vsss
The analyses were performed with a Materials
Analysis Company electron microprobe operatedat
20 kV and a specimen current of 0.025 misroamperes. X-ray lines examined and standards used areCuKcu (synthetic CuS), AgLa, Sb,La (syntheticAgSbSJ, Pb.La, SKcu(synthetic PbS), and BiZa(synthetic Bi2S3).The data were corrected using amodified version of the EMPADR VII computer
progrcm of Rucklidge & Gasparrini (1969). Results
ofthe analysa are given in Table l. Thesearein close
agreementwith thosereported by Zakrzewski (1984).
The formula is ideally Pb2+,CufSb,Bi)2-,S5, where
Sb exceedsBi and x is equal to 0.15. For a normalthe calculatized formula Pb2.6Cu6.
15Sb1.osBi0.77S5,
ed density is 6.59 g/cm3 with Z:4,
PHYSICALAND OPTICALPNOPENTTSS

Jask6lskiite occurs as lath-shaped crystals (Figs.
la, b) in galena, commonly associatedwith pyrite,pyrrhotite, marcasite,chalcopyrite, tetrahedrite andnative bismuth. The mineral is generallyfree of inclusions, but a few crystals contain small blebs ofgalena, whereas other crystals have a reaction rim
consisting of an intergrowth oftetrahedrite, nativebismuth, galena and an unidentified Ag-Pb-Sb-Bi
sulfosalt (Figs. 2a, b). Jask6lskiitecrystalsseldom
exceedl50x 300 pm. Many crystalsexhibit a goodcleavageparallel to the elongation direction. The
microhardnessl{b0y'56,basedon three indentations,falls between 148 and 185, equivalent to a Mohs
hardnessof 4. The minerals could not be isolated
in sufficient quantity for a detcrmination of density.

Frc. l.a. Elongare crystal of jaskdlskiite Cia)in a matrix of galenaGal) with anhedral pynte (py). Nicols slightly crossed.
Hole 88, 153.1. b. Severallath-shaped crystals in galenawith anhedral pyrite. Small white blebs in galenaare nativebismuth. Note tle anisotropismof jask6lskiite. Crossednicols. Hole 88, 153.1.

JASKoLSKIITE FROM IZOK LAKE. N.W.T.

489

Ftc.2.a. SEM back-scatteredimage of euhedral jask6lskiite (ja) in galena. Parts of the crystal contain a reaction rimconsisting of tetrahedrite, galena, native bismuth and an unidentified sulfosalt (s). Hole 88, 198.0. b. SEM backscatteredimage of a jaskdlskiite crystal with a reaction rim of intergrown tetrahedrite (tt), native bismuth @i), galena and an unidentified sulfosalt (s). Small blebs of galena occur as inclusions in the jask6lskiite.
TABLE
2. ,rNKdLsKtlI[: REtlEcr!illctDATA
In reflected, plane-polarized light, jask6lskiite isGrain 3
craln I
Graln 2strongly bireflectant. Reflestancepleochroism is absent (Iable 2, Fig. 3), but the strengtl of the bireflec- lnm Rt Rr itRr itR. Rl imRr Rr R2 itR, ltR,tance is suchthat the greenishwhite to greenishgrey 400 4t.7 44.7 27.0 29.9 44.6 n.4 3t.4 44.9
rrl0 41.6
2n.6
44,3 t.0
44.5 26.t
3E.4 44.8 23.5 )0.1
appearanceof the mineral in some orientations can 420 4t.5 44.3 26.6 29.3 43.9 2t.6 tt.4 44,6430 41.3
4tt.2
26.3
24.9
43.5 4.2
44.4
21.0 29.3
give a false impression of pleochroism, or pseu- {q0 4l.t 43.9 26.0 24,6 43.2 27.4 38.3
38. I
44.1 22.7 zt.t
dopleochroism.It is strongly anisotropic;somesec- 450 t 0.9 43.6 25.7 2t.3 42,9 27.5 3t.0 4t.9 22.4 28.4
tt0,727.9
42.7
27.2
43.4
25.4
37.E 43.6 22.t 2t.A
tions are symmetrisal, others asymmetrical,with the x60
470 40.4 43.2 25.t
27.7
42.5 27.0
37.6 43.4 22.0 27.7
tt2,948040.227.442.)
26.7
27.t1
24.9
37.4 43.1 2!.t
result that the sequenc€ofrotation tints can be from490 40.0 42.t 24.6 27.2 42.t 26.5 37,2 42.9 2l.6 27.1
extinction to brownish grey, greenishgrey, greenish
500 39.t 42.6 24.5 27.0 4t.9 26.3 37,0 42,6 2t,4 26.9
26.7
white, brownish to purplish gxey, brownish grey to,10 39.7 42.4 24.1 26.8 4t.t 26.1 36.9 42.4 2t.)n0 39.6 42.3 24.2 26.6 4t.6 26.0 36.7 42.t 2t.r 26.5
extinction and tlen, dark blue, slategrey, pale-bluish 530 39.5 42.2 24.t 26.5 4t.6 2r.9 36.6 42.t 21.0 26,4t+2.0
21.0 26.2,40 19.4 42,t 24.0 26,4 4t.5 U.t
16.5grey, bluish white, light grey, dark grey, purple, to. 4 [t.a20,9 26.r
19.3 t2.0 2).t 26.i 4t.3 25.7
extinction. With the analyzeruncrossedby l-2o, the560 39.2 4t.t
23.7 26.2 4t.2 25.6
. 3 4t.7 20.t 26.04t,625.94t.7
23.6
26.0
4t.
l25.
4,239.t
rotation tints do not changeexceptto becomemore t80 19.0 ttl.6 23.5 25.9 t l . 0 2 5 . 3 t 6 . l 4t.5 20.7
20.6 2r.8
40.9 25.2 36.0 41.4 20,5 25.7590 t9.0 ttl.'
2t.4 U.8
vivid. The asymmetry in crossedpolars is the strougestoptical evidencethat jask6lskiite is biaxial, since 600 38.9 ttt.4 83 2r.7 40.t 25.1 36.0 4t.3 20.4 25.54t.l
20.4 25.4
6 1 0 3t.t
41.3 23.2 25.6 40.6 24.9
t t.o 20.t 25.34t.2 23.1 25.4 40.5 24.7 , r . t
the reflectance spectra measured on three grains 620 34.7 ql.o
630 3E.623.0 25,) 40.) 24.5 35.6 40.8 20.2 25.1
could reasonably be interpreted as fitting a rrniaxial
40.7 20.t 24.9
640 38.4 40.9 22.8 25.1 40.I 24,4
mineral. In Table 2, R2 and i^R, for grains I and40.5 t9.9 2q.t
650 34.2 40.6 22.6 24.9 t9.9
24.1
40.2 rg,t 24.5
60 3t.0 40.4 22.5 24.6 19.6 23.9
3 are remarkably similar, and R' andinR' for grain
670 3 7 . t 4 0 . 1 2 2 . 2 24.4 39.4 23.7 15,0 40.0 t9.6 24.3
t7.6 39.9 22,0 24.2 39.r 2).5 34.t 39.t 19,4 24.1
2 are within lVo of these,that is, within acceptable 6E0690 )7,3 t9,7 2t,8 23,9 ?8.9 23.2 34.6 39.6 r9.2 23.9
7@ 3 7 . 0 1 9 . 4 2 r . 5 2).6 3t.6 ?3.0 t4.4 39.3 t9.0 2t.7
measruementerror for microscope photometry. It
Color
vnlu6 .elatlre to the CIE llhrmlnsi C
is relatively unusual to locate an isotropic gain in
0.306
0.106 0,m2 0.302 0.30t 0.3t2 0.305 0,035 0.3t2 0.30rr
minerala random sectionof a biaxial
sincethis mey 0.312 0.312 0,108 0.308 0.tr2 o.na 0.312 0.31t 0.r08 0.306
20.4 26.1
YX 39.3 4t.9 23.A 26,2 41.2 25.6 36.4 4t.t
ans that the grain has been cut and polished normal
477 4n476 475
474 47t
478 t+76 4n,d4n2.
2
4.4 3,t2,
54.
02.
23.
9
Pe*2.t2.
03,
9
to one of the mineral's rotation axes.Indeed, it isColor valu6 relatlee to the CIE Ulumlnot A
so unusualthat the Committeeon Symbolsand Defi0.\4t 0.44t 0.440 0.440 0.44i 0.440 0.443 0.442 0.440 0.439
n,tions of the IMA/COM has not provided a symv 0.406 0.t 07 0.40J 0.40, 0.407 0.406 0.406 0.406 0.401 0.405
25.4 16.2 41.6 20.7 2r,939.t 4t.7 23.6 26.0 4l.l
bol for this case.For this reason,in Table 2, the more Y*49t
49t
490 490 492 491 491 491 t+90 489
fd
general symbol for an anisotropic mineral that is Pe% 1 . 0 l . l 1 . 9 2 . 0 t . 2 2 . 0 t . l t . 3 I . e 2 . 1

490

THE CANADIANMINERALOGIST

15-€mbda ntn
imRr,imR
Frc. 3. R1, R2 (upper curves) andspectra (ower curves) between 400 and 7@ nm for three grains of jask6lskiite. Sampleis from hole 88, 153.1.All the spectrawere measuredrelative to a WTiC standard, Zeissnumber
314. The ,uR spectra were measured using Zeiss oil Np 1.515. Measurement procedures and equipment are as
described by Harris et al. (1984).
DATA FOR JASKOLSKTTTE,TABLE 3. X.RAY POI9DER.DIFFRACTIONIZOK LAKE, N.I9.T.
Hole 8E lt3.l
Iestr

ai.e".'

aAc.L'hkl

lest

t0

5,67
5.45
4.96
4.30

5.70
5.44
4.95
4.29
3.74).72
3.70
3.r8
3,32
1.24
3.r7
3.14
2.960
2.849
2.770
2.752
2.744
2.529
2.278
2.2702.26)
2.192
2,t50

130
2r004040 2 , 1 2 025b 2.041

3203.7)9040).59
3,13
3.24
3.t6
3.14
2.957
2.842

100

2.75t60

l02,523,02.268

40

2.192
z. \1trinteEitis

l0150240310
t2l
131
250
150
23t
260
301
241

dAm6.

1.981
t.964

t060

t'I6t

40

r.724

dAcalchkl

2.116 081
2,0q3 002
1.979 0100
t.979 Vl
t.979 501
1.963 550
1.900 45r
1.899 t90
r.a95 531
1.884 500
r.789 312
1.781 o.tol
1.760 r'iol
r.752 3t00
t.7zz Fr

270L7t)5t
421
431
271
460

gareB
estimadirom
114.6 mm GandolJt
Pattem(). CuKa = 1.54178A)
emDloyinc Ni llltered cu Ediatim'tt+.6 mm-. DebyF-Schffierpowder crera'
Cu EdiBtion' Ni fllter (lCuKo = l.54l7EA)i admixed galeE lin$ omittqr' b = br€d llnes
sindexed vith a = lL.3l' b = 19.79 md c = 4.087A

measurablyisotropic R' is used (Criddle 1980)'
Color values for the three grains show excellent
aexeement between the observed and calculated
c6lor, x, in all instancesbeing iq the green sectbr;
the low?eqo confirms the eye's impressionof low
saturation of this tint.
X-Rav Srulrcs
Two fragments of jask6lskiite, dug out of apolished section,were examinedby precessiolX-ray
diffractometry employing Zr-filtered Mo radiation.
Precessionphotographs of. hlfi, hkl and 310'r'.tlC(with 310'eas the diat axis) were taken of one fragment and 0kl* 2kl, hjl- h3l (with C asthe dial axis)
were taken of the other fragment. The small size ofthe crystals necessitatedone-weekexposuresfor all
final photographs.
Jask6lskiiteis orthohombic, with 4easured cellparametersa 11.4,b 19.8and c 4.08 A. Systematicabsences,h\l wilh h + I = ?n and 0kl with k = 2n, dictate either Pbnm (62) or Pbn21(33) as permissible
space-gloups.

JASKOLSKIITE FROM IZOK LAKE. N.W.T.

The X-ray powder-diffraction data for jask6lskiite from Izok Lake are listed in Table 3. Thesedata
are in good agreementwith those obtained by Zakrzewski (1984) on material from Vena, Sweden.Refined unit-cell parameter!, basedon 13 powder lines
between4.30and l.7Z A for which unambigousindexing was possible, ^ gave a I l^.31(l),b 19.79(2), c 4.087(4) A, V 914.8 A3 andaib:c=0.572:l:O.2M.
AclnlowtrlcsN{ENTs
The authors are grateful to John Heslop, Kidd
CreekMines Ltd., for assistingone of us (DCI{) inthe field work during which the specimenswere collested and to Kidd Creek Mines Ltd., for agreeing
to the publication of the data. We also thank Y.Y.
Bourgoin, Canada Centre for Mineral and Energy
Technology (CANMET), for preparation of thepolished sections.

49t

Cupor.B,A.J. (1980):Editorial policy for the second
iszueof tle IMA/COM QuantitativeDataFile. Can.
Mineral. lt, 553-558.
Henrus,D.C., Ronrr.rs,A.C., Tnonrn,R.L., Cmool:e,A.J. & Srem.Bv,C.J. (1984):Kiddcreekite,a newminoal species
from ttreKidd Creekmine,Timmins,
Ontario and from the Campbell orebody, Bisbee,
Arizona. Can. Mineral. ?2,2n-232.
Moxey, P.L. & HssLop,J.B. (1976):Geologyof theIzok Lake massivesulphide deposit. Can. Mining
J. 97(5),24-n.
Rucxr.rpce,J.C. & Gaspannrm,E. (1969):Specifications of a computerprogramfor processingelectron
microprobe analytical data: EMPADR VII. Dep.
Geol,, Univ. Toronto,
Zernzewsrr,M. (1984):Jask6lskiite,a new Pb-CuSb-Bi sulfosaltfrom the Venade,posit,Sweden.Caz.
Mineral. 22, 481485.

REFERENCES
Bosrocr, H.H. (1980): Geology of the Itchen Lakearea, District of MacKenzie. Geol. Sum. Con. Mem.
391.

ReceivedAugust9, 1983,revisedmanuscriptaccepted
December21, 1983.