Canad,
ian IVIineralogist,
Vol. 11,pp.85l-860(1972)TEUCOSPHENITE
FROMMONT ST. HII.AIRE,QUEBEC
c. Y. CHAOaro DAVID H. WATKINSON
Department of Geologg,Carleton Uniuersitg, Ottawa, Ontaria K/S 586

AssrRAcr, Leucosphenite occws as small, colourless to pale blue, elongated tabular crystals andwedge-shapedcrystals in the pegmatites and thermally metamorphosed inclusions in thenepheline syenitg Mont St. Hilaire, Ouebec. It is mainly associated with microcline,
albitg aegirine, calcitg and quartz.
Leucosphenite crystals from Mont St. Hilaire display a variety of habits commonlywith {100}, {010}, {001}, {110},^and rarely with {130}. The space group is C2/m-;
g =9.781, b = 16.854 c = 7.2081gB = 93"16'. Density = 3.065(5) g/cms. Hardness=
6-6.5. Cleavages {010} and {001} are fair. It is optically biaxial (+) ; G = 1.643,
8 : Jr05f, V : 1.681,2V :'16"" in sodium light. ThJoptical plane is normai'to (010j
and YAc varies with a maximum f9'. It has marked dispersion with r ) u.
, .,Electron microprobe analysis gave SiO2 53.66; At2O3 0.11; Nb2O6 0.77;, TiO21452; BaO 11.98; CaO 0.06; total Fe as FeO 0.04; Na2O 11.61; Ksd 0.51; MgO,MnO,-Zfr2 and Y2O3 not found; total = 99.86/e including 6.670 B2O3 determined byw-et cllemistry. The analysis recalculates to Naa.1IQ.12Baa.s6Cae.61Ti2.o0Nbo"06B2"08
Alo.o2sie.8103o.

INrnoouctlolr

Leucosphenite was originally described by Flink (1901) as a whitewedge-shaped mineral occurring in the pegmatite veins in the Narsarsuk
region, Greenland. Flink gave BaNar(TirOr) (Sirou)u as its ideal formula.
Leucosphenite was later found as a widespread mineral in the Green River
formation in Northeastern Utah (Milton et al. L954) and Wyoming(Milton 1957). On the basis of chemical analysis of the Utah mineraland spectrographic analysis of the type Greenland crystals, Milton andothers proposed a formula, CaBaNauBTisSieO2n, including boron andcalcium as essential components. Yefimov & Katayeava (1959) reported
the occurrence of leucosphenite in the pegmatite veins of the Inaglinaultrabasic-alkaline massif, South Yakutia, USSR; they did not find calcium in the Yakutia leucosphenite but confirmed boron as an essential
component and assigned the mineral a new formula, NarBaTirBr(Siou)ro.
This formula was later verified by crystal structure analysis (Shumyaiskaya ef a/. 1968) and was adopted by Strunz in the fifth edition of his
Mineralogische Ta.bellen (1970). Chso et al. (1967) reported a newoccur?ence of leucosphenite at Mont St. Hilaire, Quebec ; the description

852THECANADIAN

MINERALGISTof this rare mineral from Mont St. Hilaire now forms the core of thispaper.
OccunnsNcr
The general geology of the Mont St. Hilaire area has been describedin detail by Dresser & Denis (1944) and summaized by Chao et al.
(1967). Leucosphenite was found in small amounts in the peg@atites andin the wall-rock inclusions in the nepheline syenite of the Mont St. Hilairepluton. The inclusions of shale interbedded with thin layered limestone
were metamorphosed to greenish grey or grey homfels and to siliceous
marble. Well-formed, tabular, pale blue leucosphenite crystals up to I mmmFrc. 1. Crystal drawing of leucosphenite from Mont St. Hilaire, Quebec,
showins a{100}, b{010}" c{001} andrn{110}.

Frc. 2. Tabular leucosphenite crystals(Imm in length), elongated along aand flattened on {010}.

Frc. 3 (bottom). Wedge-shapedleumsphenite crystal bounded by {001}'{010}, {130} and narrow {100} (ength of crystal = 3.5mm).

LEUCOSPHENITE

853

in length were found in pegmatitewith microcline,albite, aegiring sodalite
and minor amountsof ramsayite,elpidite, polylithionitq ancylite, pyrrhotite and pyrite. An inclusion in the syenite contains leucospheniteas verysmall tabular crystals (average0.2 mm) lining a small vug. The minerals
surrounding the vug are microcline, albitg calcite, fibrous ramsayitq fineneedlesof aegirine and a hitherto undesci.ibedmineral UK#6 (Chao etal.1967). Leucosphenitewas also found in the quarr. veins in the homfels
as pseudohexagonalcrystals up to I cm across,associatedwith lemonyellow narrarsukitg purple fluorite, calcite, a recently decribed newmineral, carletonite (Chao 1971) and minor amountsof ancylite, aegirine,ramsayitq molybdenite and galena.

Cnvsrarr.ocRAPrrY
Leucosphenitecrystalsfrom Mont St. Hilaire display a variety of habits.
Somecrystalsare elongatedalong c, boundedby {010}, {001} and {110},in order of prominence (Fig. 1) ; t010) is sometimesthe only prominent
form and {100} is either absentor very small, resulting in a tabular habit.
Somecrystalsare tabular but distinctly elongated along a with prorninent{010} and small {00i}, {110}, and {100} (Fig. 2). A few crystals areelongatedalonga but boundedby {010}, t00l}. tl00} and extremelywelldeveloped{130},giving riseto a wedge-shapehabit (Fig.3). For al1crystals
examinedthe forms {021}, and {22I), reportedto be common on crystals
from Greenland and USSR, are characteristicallyabsent.The (hft0) faces
on large crystals (up to I cm) from Mont St. Hilaire are often heavily
striated along c. Small crystals,although not apparently striated, always
gavemultiple signals on the optical goniometer,rendering accuratemeasurements of the interfacial angles difficult.
Weissenbergand precessionphotographsof severalsingle crystalswere
prepared with CuKo and MoKa radiations respectively.Systematicextinctions were found to be consistentwith those required by spacegroups
C2, Cm and C2/m. Morphologicalstudiesof the Mount St. Hilaire leucosphenite revealed no symmetry lower than 2/m. Crystal structure analysis
by Shumyatskayaef al. (1968) indicated the spacegroup to be Cm but
in a later refinement of the stmcture (Shumyatskayaet al. l97l) C2/m
was adopted as the correct spacegroup.
The preliminary cell parametersobtainedfrom the single crystal photographs were refi.nedby a least-squaresmethod (unpublished program byA. W. Hounslow & G. Y, Chao) using r-ray powder diffraction data

854T}IE

CANADIAN

MINERALOGISTTarrs 1. X-nav Poworn Drrrnacnox ParrsRN oF LrucosPgglrra, Monr Sr. ttramr(114.6 mm carnera! CuKa radiation (l = 1.54lSA), Si standard, visual irrtensities)
doo".(A)90d'4cdcdc.(A)hkl(8.4li95

110sso2o001 vw;I I,I,

\a.ant7.i966c.otrt5.47265.3501
2A

AeTn !4.8826
I4.s69z| 4.247

100

q'22n

4W2
3.980
3.936
3.728

l0
10
2030
?0DU

30
3030
1060

r0

1 z*.zrJJ, rt er
Idoo..(A) d""".(A)

40t cle!'vv

40

2132

021 vw
1llvw
m2ns
130
220 vs

10

2.616
2.577
2.460

ArA
ur+u

ZOt Yw
Tgt m.s
131 m
201 mss
Vzt
041w
002 m
221s
ItZvss
022
II2s
310 w
2.4n s

2.98352.9789, sR!
\ 2.9574
2.9341
2.930
23338, col I 2.8937\ z.szoo( 2.8622
z'dobt z.sssa\82Wgtt.ln =.1 powder , I*:

2OZ
24tlgZ
15115124131182202

r 2.8165 330

30m

2.3%6
2.3%8
2.3072( 22868I| 22783|I 227n{sz msl2.nn

40i

s4zt;/,JJIw

2.%5
2.2A1
2.216

L26M
22540
2.n23
L2145
L2142

Mtt,''..

!2,2f,B3
I 22003

Tzt
17I
462
2og

ms
ms
r'w
v"w

J5lm

2.434

2.Wr
2.3381
Z.JJ

2.327<c2.30640,tqnc5tz

s400
vs%02u mw
Tsz abs
003 abs
152 wvmabsw
420w
242
Tts vq/
170 msNtw
312 m
023 m
261 vs
113 msvw
ss\.w
mssvs
ms
mss

222
Aa
222
5gt
061
331

i z.aogo 060
2.80862.73632.67502.66782.61682.57992,458824413
2,43482.43242.40782.39892.36382.3531
2.34/19

Iss
mvsmw
msmIs

41519
4.0874
3.98m
3.93-/6
3.7%,4
3.6361
3.59833.569
3.5674
3.3?1
3.3?103.306
3.30933.250
3.2533
3.1960f "'-"""
3.1899e reo )

\ s.rsog r5o10hKI

I II

I Weissenberg.
us = very strong, s = strong, ms = medium to strong, zl = medium, wm = weak
to uediurn, ra = weak, vlt = very weak; abs = absent.

855

LEUCOSPHENITE(Table 1). The indexing of the powder pattern was basedon comparisonof the observedand calculatedd-values,using single crystal photographs
as a guide. The refined values and their estimatedstandarddeviationsare
incorporatedin Table 2.
The axial ratios given by Flink (1901), 0.5813: I :0.8591, and by
Yefimov & Katayeava (1959), 0.5783: 1 :0.8499, correspondto a unit
Tesr,s 1. X-nav PomsR Drrrnacrrorv ParrsRN or LnucospHrr.rrr:e, Mour Sr. llnanx(114.6 mm camera, CuKs radiation (1, = 1,54184), Si standard, visual intensities)

tpdc.a n c(. ' A )

hkttw

421
Igs, rAo 12.1766\ 2.1666 332

w
ms

do.D s 6\.'

2.t94

<5o f on20

2.105<l)2.077

10
l0l2.1316\ z.rzsr

L0u7
2.07592.W44zyIL

Lt124
2.10682.1061

I z.otsz

1.972<51.95210

1.933

wln133 wm
Mwm
080s
2Ags043s, nAs [2'0437\2.M32
2.02t9, orR tl0%2.40042.00041.99051.97271.9723
1.96881.9525
1.94821.94011.93571.934
1.93381.9268
r.9172

Aaz m- , , vw
NZ ms
223 wr081
s422 mNZw
441 vw
262w

p

do b s . '( h' d51899<51.882I<51.84S

101822
1.799
20
l.7U
<5L765<520
1.735
51.703
1.684
20Tzz m 10 r.6&5tg m
1.628
10
1.610
402 ms5lqsm201.594
1.580
172 we<551.562
510 m
1.5410370 m
1.527
10n0vw
Tss m 10 1.515
352 we many more lines
42wm

elc.'

6 \'hklIw

r 1.s004 511 m
1 r.8996 531 mn
1.88s 5Zr
1.88391.873?
r.8724
1.8690t.8622
1.85761.8536
1.8471

243 m
Dl] wm
ggg w
313 m
vw
@m
2f1
371 m
511 m

856

THE

CANADIAN

MINERALOGIST

distanceon c doubled relative to that chosenfrom the structural cell. The
indices given by these authors can be transformedto those referred to inthis paper by the matrix 100/010/00+.
PHvsrcer enp Oprrcer. Pnoprnrrns
Leucosphenitehom Mont St. Hilaire is colourlessto very pale blue
with a vitreous luster, transparent in small crystals and translucent inlarge ones.The averageof three determinationsof density at 23oC, usinga Berman balance and toluene, gave D : 3.065(5) g/cmu. Hardncs on
the Moh's scale is 6-6.5. Cleavage{010} and {001} are fair. Fracture isconchoidal.
The refractive indices were measuredby immersion at 23oC on a flatstagewith a sodium light source.Single crystals with known orientation
Tasrr 2. Prrvsrcal alvp Opncar PnoprnrrBs or Lrucospurrvrm
Mont St. Hilaire
QuebecoI
y-a

r.643
1.657
1.681
0.038

Yakutia,USSR
Yefimov &Katayeava(1959)

Narsarsuk,
Greenland
Rink (1901)"

1.64851.6640r.69100.0425t.w5
l:66@
1.68780.043377'4'(calc.)

2V

760

780

Optical Sign

(+)

(+)

(+)

Dispersion

r>u

r>u

r>u

Z=b

Z=b
Y Ac-- -3'21'(crossed)
Orientation

Z=b(max.)

YAc-f9'Parallel extinction(t)(-)

Hardness

ffi.s

Density (e/@8)

3.065(5)

6.1
3.0s
9.79
16.84
724
9329

Sign oI Elongation

o(A)
b(A)
c(A)
B

(1)
e.?8r
l6.ss(2)7208(l)93"16(1)',

I Refractive indices are for "yellof'p.431).

(-)
6.5
cn<
9.76
r6.@
7.10
93023',

light, Cell parameters from Strunz (1970

LEUCOSPIIENITE

857

from r-ray diffraction or optical goniometrywere used.All Cargille liquids
used were checked by
Abbe refractometer. The uncertainty of the"o to be lessthanmeasurements
was estimated
I 0.001.The optic angle wasdeterminedby Kamb's method (Kamb 1958) with a large uncertainty of-f 50, due to the poor resolution of the isogyres.The results of this study
are given rn Table 2 where they are compared with properds of leucosphenitefrom Greenland and USSR. The refractive indices of the Mount
St. Hilaire mineral are considerablylower than those of the Yakutia andGreenland minerals, particularly for B and y. The extinction angle YAcof the Mont St. Hilaire mineral is variable over a large range from crystal
to crystal, and sometimeseven within the sa:ne crystal.
Cnrurcer Auelvsrs axo Fonmur.e
Leucosphenitewas analyzed using the Cambridge MK 5 electron
microprobe for the following elementsusing the standardsshown in parentheses: Fe (metallic iron) ; Mg (synthetic phlogopite) ; Ca (calcite) ;Si, Al and K (microcline); Zr (synthetic zirconia) ; Na (jadeite) ; Nb(metallic niobium) ; Y (synthetic yttrium iron garnet) ; Ba (syntheticbarium ferrite) ; Ti (ilmenite) ; Mn (metallic manganese).Analyseswere
madeat 15 KV acceleratingvoltage (20 KV for Y and Ba) and a sample
current of about 50 nanoamps (about 30 for Na and 7'r) vsrng a fi.nely
focussedbeam. Ten- or twenty-secondcounts v/ere cpllected and thepolished grain mount was moved about 10 microns before another of theapproximately eight sets of counts was taken for core and margin of eachof six grains. Ten-secondcounts for Na and Zr were collectedwhile thespecimenwas translated at 10 pm per minute becausethe specimen
cunent and counting rate for NaKo-radiation decreasedslighdy using astationary spot.
for generation (atomic numThe x-ray data were computer-correctedber), absorption and fluorescenceefiects using the program written by
Rucklidge (1967). The averageanalysis is given in Table 3 with B,O.
determined&emically by B. Ingram on a 200 mg hand-picked sample.
The variation between core and margin and among grains was approximately equal to the standard deviation of counts for the seriesof about
8 counts at any one site. Thus zoning is not apparent from microprobe
analysis.The analysesof the Yakutia and the Greenland leucosphenites
are also listed in Table 3 although the latter is apparently in error inomissionof BrO, as was pointed out by Milton et al. (1954).
Formula of the Mont St. Hilaire leucosphenitecalculated on tle basisof 30 oxygen atoms per formula (Table 3) deviates only slightly from

858

T}IE
Talrs

sio2

CANADIAN

3. Clrrvrrcar

Al2o3

53.66
0.11

Bzos

o.o

Fe2O3

Yzos
Nb205
I I\J2

BaO
CaO
SrO
FeO
Mgo
MnO
Na2O
KzoZt(JzHzo
Total

not;d
0.77
14.52
11.98
0.06
0.04
not found
not formd
11.61
0.51
not formd

MINERALOGIST

ANai.ysss or LrucospHrNrrs

54.3
not found6.360.28
0.1
13.92
13.00
not found
0.035654

SzLZt

u*

gn
13.75

13.84

1;

t;

ts.ss

0.15
10J0
0.79
"
not tounct

99.86

u.5b

3.50
0.31
99.40

l00s0

Anmic Ratios to 30 Oxggen Atoms

SiA]
B

9.81

0:02
2.08

Fe3 +M
Ti
Ba
Sr
Fe, +

0.06
2.04
0.86
0.01

10.00

^
0.M
0.00i
1.93
0.94

2.00

iov

0.002
0.005

MoNa
K
D@lc.
Dooa.
.

10.03

4.11
O.I2
3.078

3.065(s)

*,
3.83
0.18
3.m2
3.089

1. This study. Electron microprobe analysis by DHW;Total Fe as FeO.
2. Yefimov & Katayeava (1959).
3. Flink (1901).
4. NaaBaTi2BzSiloOBo.

*o
3.05
BzOg by B. Ingramo U.S.G.S.;

LEUCOSPTTENME

859*. Density, calculatedwith the cell
the ideal formula NanBaTirBrSi,.oOro
parametersobtained in this study and Z: 2, is 3.078 g/wr', in good
agreementwith the measuredvalue 3.065(5).
The Mont St. Hilaire leucosphenitecontains slightly lower Si and Ba
but higher B and (Na, K) than does the ideal composition,indicating
partial substitution of Si by B and Ba by (Na, K). The balanceof charges
is probably satisfiedby coupledsubstitution of Ti and Nb.
The high ZrO" antent (3.50%) in the analysis of the Greenland
leucospheniteis probably due to contamination by elpidite which wasreported by Flink (1901) as closely associatedwith the Greenland leucosphenite.
AcrxowlrocEMENTs
We wish to thank B. Ingram of the United StatesGeologicalSurvey
for the BrOu analysis and ProfessorsC. Milton and A. Pabst for theirinterest in this work. H. Budgen generouslyprovided some of the leucosphenite specimensused in this study and Miss J. Baker provided technical assistance.This work is supported by National ResearchCouncil
grants 45113 to GYC and A7874 to DHW.
Rsrrnrwcrs
Cnao, G.Y., Hanns, D.C., Hounsr.ow, A.W., Mauoenwo, J.A. & Panneurr, G. (1967) :Minerals from the nepheline syenite, Mont St. Hilairg Quebec, Canad. Mineral.
9,109-123.
Cnao, G.Y. (1971): Carletonite,KNa+Ca+(COs)gisOls(ROH).HzO, a new mineralfrom Mont St. Hilairg Quebec.Amer. Mineral. 56 1855-1866.
Dnxsan" J.A. & Drmus, T.C. (1944) : Geology of Quebec. Quebec Dept. of Mines,Geol. Report 2, 469-470.
Frwr, G. (1901) : On the minerals from Narsarsuk on the Firth of Tunugdliarfik in
Southarn Greenland. Medd. om Gronland 24, 8-273.
Kerr,r4WB. (1958) : Isogyresin interfermce frgares.Amer. Mineral. 43, M-IA67.
Mnrom, C., A:or.no4 J.M. & SHrnwoo4 A.M. (1954) : New occurrenceof leucosphenite,in oil shale from Utah (abs.). Amr. Mineral. 39, 337.
Mnrox, C. (1957) : Authig:nic minerals of the Green River Formation of the Uinta
Basin, Utah. Guidebook to the Gmlogy of the Uinta Basin, Otto G. Seal (ed.),8th Ann. Field Conf., Intermountain fusoc. of Pet. Geol., 136-143.
Rucrr:oc4 l.C. (1967) : A computer program for processingmicroprobe data. low.
Ceol. 75, 726.
Snuurarsrata, N.G., Vonor.rrov, A.A. & Prerrwro, Yu. A. (1968) : The atomic structure of leucospheniteNa3Ba2Ti4O4[B4SizoO66].
Sou. Phgs.-Crgst.13, 130-131(translated from Kristallograftya 13, 165-167,1968),* The structural formula given by Shr.rrnyatskayaet aI. (1971) is NasBa2TiaOa[Si16(Si,B)8O60].The parenthesesemphasizethe disorder of Si and B in only one of
the three eight-fold tefrahedral sites.

860

THE cANA-DIAN MrNERALocrsr

Snuvr:ersrata, N.G., Vononrov, A.A, & Bnrov, N.V. (1971) : X-ray difiraction studyof leucosphenite. Sou. Phys.-Cryst. t6t 416-422 (translated Erom Kirstallograflga 16,492-4W,r97t).
Srnuwz, H. (1970) : Mineralngische TabeIIm. Akad. Verlagsges,Leipzig.
Yrrrmov, A.V. & Karernev4 Z.T. (1959) : The first dixovery of leucasphenite in theUSSR Doklad. Acad. Sc,. USSR 129, 1169-1171(translated from Doklad. Akad.
IVauk SSSR 129, 896.-899).
Manrtseript receiuedOctober 1971,emend,edlarunrg 1972.