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Canadian Mineralogist
Vol. 12, pp.342-346 (19741
BU.RBANKITE FRO'M MONT ST. HILAIRE, QUEBEC
T. T. CHEN AND G. Y. CHAO
Department ol Geologl, Carleton University, Ottawa, Ontario KIS 586
AssrrAcr
Burbankite occurs as small colorless, yellow or
pink, dihexagonal prismatic crystals embedded in
analcims or natrolite in the miaroles and pegmatite dikes in nepheline syenite, Mont St.
Hilaire, Quebec. It is commonly associated with
microcline, aegirine and minor amounts of calcite, siderite and ancylite.
The space group symmetry of burbankite is
P6smc wilb a = 10.5L4 and c : 6.520A. The
mineral has a hardness of 4 and a distinct prismatic cleavage. It is optically uniaxral, oo - 1.616
61d eo - 1.597.
analysis gaYe
Average electron microprobe
NagO 8.30; CaO 12.03; SrO 32.35; BaO 11.02;
CezOt 2.I2; NdzOs 0.13; Dyqoa 0.08; Yb2Og
0.10; total 66.1.3%. Assuming the stoichiometric
amount (33.17%) of COz the analysis recalculates
With Z =2'
to Na1.7sca1.aeSr:.o8ao.a8REo.ro(CO")0.
density (calc) - 3.50 g/cms.
NaaCa$r:(COr)o with the burbatrkite structure
was synthesized at 1.5 kb and 500oC, indicating
that rare earth elements are not essential in burbankite. Ba-bearing burbankite was also synthe.
sized but the extent of the Ba substitution is uncertain.
proximately 0.5 atom per formula) and RE for
Ca up to 15.1 wt./o (approximately 0.7 atom
per formula).
Ths occurrence of burbankite at Mont St.
Hilaire was first reported by Chao et al' (L967)Studies on this burbankite indicated that its
composition is much closer to the ideal composi'
tion than burbankite from other localities.
OccunnBucr'
At Mont St. Hilaire burbankite occurs in
small quantity as small, long-prismatic crystals
embedded in analcime and natrolite in miaroles
and pegmatite dikes in nepheline syenite. The
burbankite is commonly associatedwith micro"
cline, aegirine and minor amounts of calcite,
siderite and ancylite. Some burbankite crystals
aro partly altered on the surfaces to ancylite. A
few crystal molds of hexagonal prismatic habit
similar to that of burbankite were noted. These
hollow crystals are partly filled with minute
crystals of ancylite and a reddish brown pow'
dery material suggestingcomplete alteration and
removal of the parental burbankite.
INTRODUcTIoN
Bur.bankite was first described by Pecora &
Kerr (1953) as yellow hexagonal crystals intim'
ately intergrown with ancylite in the carbonate
veins of shonkinite at Bearpaw Mountains, Montana. It was later found as pink fibrous spheroidal aggregates in the lacustrine deposits of the
(Milton
&
Wyoming
Green River Formation,
Fahey 1960), and as irregular veinlets and hexagonal crystals in calcite-dolomite veins in the
Vuori-J[rvi pluton, USSR (Borodin & Kapustin
1,964\, The chemical formula of burbankite was
originally propoeed by Pecora & Kerr (1953) as
Na"(Ca,Sr,Ba,RE)n(COa)r where RE represents
total rare earth elements. Recently, from their
crystal structure analysis of burbankite, Voron'
kov & Shumyatskaya (1968) established the
structural formula to be A"Bu(COa)s, where l :
Na, Ca and B : Ca, Sr, Ba, RE. PovarennYkh
(1972, p. 611) assigned burbankite the ideal
formula (Na,Ca)(SrCa)(COs)s and noted that
Ba may substitute for Sr up to 13.6 wt./p (ap-
X-nev CnvsrALLocRAPrrY AND PHYSTcAL
PnoPsnrlEs
Eight single crystals were studied by precession and Weissenbergr-ray methodswith MoKd
and CuKa radiations respectively. The diffrac'
tion symmetry and systematic extinctions a$
shown by the r-ray photographs are consistent
with those of the spacegroups P62c, P6"mc and
P6/mmc. Although P6s/mmc was adopted by
Pecora & Kerr (1953) and by Borodin & Kapustin (1964), piezoactivity study and crystal struc'
ture analysis by Voronkov & Shumyatskaya
11968)ascertainedthe correct spacegroup to be
P6smc.
The cell parameters obtained from single
crystal photographs were refined by a leastsquares method using powder diffraction data
(Table 1). The indexing of the powder pattern
was based on the observed and calculated dvalues using single crystal photographs as a
guide. The refined valuesare a - 10.514(3)and
342
343
BURBANKITE FROM MONT ST. HILAIRE
DATA0F BURBANKITE
DIFFRACTI0N
TABLEl. I-RAY P0l,lDER
5Jmtne!r
c
Burbankl
te
( casr2)( c03) 5
( Na2ca)
M o n ts t . H i l a i r e
,9,fl
J
4obsA
acal
4obs^
hkl
cA
2
9.086
9.103
I' 10001 9 . 1 0 5
5
5.238
5.276
5.301
'l
t0
5.257
'I
4.538
4.533
200
4.553
6
5.IJJ
3.732
201
t
3.430
3.444
210
3,441
I
3.230
J.ZOU
3.258
002
8
3.027
3.04r
211
3.043
4
2.740
2,754
301 2 , 7 5 2
l' 100
2.629
8
2.651
202
2.621
2.631
10
2.628
220
z
2.344
2.354
I
2.355
3ll
1
2.268
2.278
400
?.276
I
2.209
2.221
2.220
30?
b
?.139
5
2.150
401
2,149
a
2,094
2.11?
103 2.114
z
3
2.034
2.046
222 2
'I . 0 4 6
I OeO
4
1
L
410
.987
'l . 9 8 2
'I
.945
.960
203
1.96t
1.856
I .600
1.867
402
at5
1.838
1.748
| ./JO
1. 7 5 9
322
'I
,^
.698
412
1
'I
'I . 6 9 7
3
1
.
6
6
4
421
.664
'I .657
'I
.580
1. 5 8 6
511
.586
1.561
1.570
1.572
403
I .JJ/
204
,
I .520
1
422
'I . 5 2 2
1.453
.459
1.460
43r
C U . K Er a d l a t l o n
(f-l.54lUAli
51 stanoaro.
Il4.bllm cilerai
s y n t h e t i c ( N a r c a ) ( C a S r 2 ) ( C 0g3r)o5w na t I . 5 k b , 5 0 0 " C .
c - 6.52OQ)A, comparable to the values reported for burbankite from other localities
(Iable 2).
The colour of the St. Hilaire burbankite varies from colourless, pale yellow to pink. The
mineral has a vitreous luster, a hardness of
about 4 and a distinct prismatic cleavage. The
crystals are dihexagonal prismatic with a
shallow pyramidal termination. The prismatic
faoes are heavily striated parallel to c. The mineral effervesces strongly in dilute (IO%) IJCI.
The optical properties of the St. Hilaire burbankite measured in Na-light at 25oC on a spindle stage are given in Table 2 where they are
compared with properties of burbankite from
other localities. The St, Hilaire burbankite is
characterized by low refractive indices that are
comparable to the refractive indices of synthetic
Na,CaeSr:(C0s)5.
OF BURBANKITE
ANDOPTICAI.PROPERTTES
TABLE2. CELI PAMMETERS
:tfil
d-e
?:''*3{
l.
2.
3.
4.
10.514(3)
6,\nQ)
1 . 6 1 6 0)
1. 5 e 7 0)
0.019
3 . 5 0( c a lc )
ErecrnoN Mtcnornose ANer-vsrs
The St. Hilaire burbankite was analysedusing
a Cambridge MK5 electron microprobe. A preliminary qualitative scalr was first made to survey the elements present for the selection of
standards. The standards used were pyroxene
(for Ca), jadeite (Na), celestite (Sr), benitoite
(Ba), bastnaesite (C€,La"Sm,Pr), anorthite glass
(Al), NdAlO, (Nd), DyrAlsOr" (Dy), YbaGarOu
(Yb) and metallic Nd and Gd. Analyses \{ere
made using a defocusedbeam at 15 kv accelerating voltage and a specimen current of about 5O
nanoamps. The intensity data were processed
by computer using the program written by
Rucklidge & Gasparrini (1,969).All grains analysed were first checked for identity by l-ray
diffraction using a Gandolfi camera.
The averaged analysis of burbankite is given
in Table 3. COz was not analysed due to the
small amount of material available. Assuming a
stoichiometric amount of COs, the analysis was
recalculated, on the basis of 5 oxygen atoms
per formula (excluding COr), to
(COs)s.
(Ctu.esSts.oD
(Nat.reCar.oz)
tu.a'R.Eo.ro)
OF BURBANKITE
ANALYSES
TABLE3. CHEI.IICAL
Na20
A1^0^
Ca0
5r0
Ba0
ceZ03
LaZ03
Gd203
Nd203
srnz03
Pr^0. J
3.54-3.58
3.25(calc)
lbnt st. Hilaire, R.I. at 25oc, Na-llght, splndle atage.
tilontana(Peora & Kerr 1953).
V u o r l - J e r v i p l u t o n , U S S R( B o r o d l n & K a p u s t i n 1 9 6 4 ) .
S y n t h e t l c t t a r c a r s r r ( c 0 3 ) 5 . R . I . a t 2 5 o C ,N a - l i g h t .
JZ.JC
11.02
2.12
n.q.
n.o.
0.13
I
v.z5
'I
3.46
19.42
'I
3.56
9.48
n.q,
n .o .
Nb^0"
- za
Yb?03
co2
Kzo
0.08
n .o .
0.'10
(33.I7)
si02
Fe203
M9o
'1.
(ee.30)
I 2 .1 9
0Ao
9.8n
9.96
I4.60
1,,,
)
a5
Dyzoe
D
' 2N - 5
'10.41
'r0.53(5)
t 0 . 4 7 7( 2 )
HZ0!
(2)
6.48
6.4s6(3)
6.47
'I
)
5(r)
. 6 3 2 - 1 . 6 3 5 r'I.61
1.627
1 . 6 m - 1. 6 2 3 .596(1)
toEal
0 . 0 12
0.019
0.0r2
l.au
I.
8.30
n .o .
12.03
32.55
32.14
0.15
0.16
0.03
0.I4
0.12
0.18
0.24
0.74
0.06
0.to
oo ?l
2.60
98.42
M o n ts t . H i l a i r e , Q u e b e cY, e l l o ! ,cl r y s t a l ; c 0 2 c a l c u l a t e d .
2. Montana(Pecoraand Kerr, 1953); analysis includes 4%
inpuri ty.
3 . V u o r i - J $ r v i. p l u t o n , t S S R . ( B o r o d i na n d K a p u s t i n ,1 9 6 4 l i
a n a l y s i si n c l u d e si m p u r i t y .
344
THE
CAN,4DIAN
With this analysis and assuming Z :1,
the
calculated density, 3.5'0g/c,m3,is well within the
range of values reported for burbankite from
other localities (Table 2). The small deviation
of the total of cations from the ideal number
(6) is attributable, in part, to errors in the analysis of Na. It was noted that during the analysis,
Na counts decreasedwith .time, tending to give
lower Na values.
The St. Hilaire mineral may be distinguished
from burbankite from other localities by its
high Sr and low total rare earth contents Clable
3). The association of low rare earth content
and low refractive indices for the St. Hilaire
burbankite falls in line with the observations by
Borodin & Kapustin (L964) thal the refractive
indices of burbankite increase with increasing
rare earth content.
Several crystals of burbankite, although optically clear, were shown by x-ray diffraction
melhod. to contain ancylite and carbocernaite.
Electron microprobe analyses of these crystals
consistently gave very high values of Ce:Os and
La2Os,up to a total of. 46/s.
SyNrneses op BunneNrItB
In order to determine whether the rare earth
elements are essential in burbankite, an attempt
was made to synthesizerare-earth-free burbankite. Stoichiometric starting materials were prepared from reagent-grade CaCOg, NaCOr,
BaCO' and SrCO". The mixtures were finely
ground to ensure homogeneity. For all the runs,
about 70 mg of the mixture and 25 mg HzO
were sealed in a gold tube and treated hydrothermally at 1.5kb. and 500oC for a week. The
products were quenched, examined under a
polarizing microscope and identjfied by r-lay
powder diffraction. The starting compositions
and their products are listed in Table 4. Most
of the runs were repeated and in all casesidentical results were obtained.
Of all ttre runs only NaCa:Srr(CO3)5 (run
l, Table 4) consistently yielded single-phase
products that gave an .r-ray powder pattern
identical to that of natural burbankite (Table
1). Calcium-free and Sr-free runs (5 and 6, Table 4) yielded no burbankite. All other runs
contained Ba and yielded burbankite plus benstonite with or without strontianite.
The crystals of synthetic Narcarsrz(Coa)s are
small (0.03 x 0.01 x 0.O1mm) prismatic, with
shallow pyramidal terminations (Fig. 1) resembling the natural crystals. The refractive indices
of the synthetic compound are comparable to
those of the St. Hilaire burbankite, whereas the
cell parameters are considerably smaller (Table
MINERALOGIST
OF BURBANKITE
SYI{IHESIS
TABLE4. HYDMTHERJ.IAL
( 5 o o oI l 0 o c , 1 . 5 k b , 7 d a y s )
( numberof-formirla weights)
Run I'la2C03 CaC03 SrC03 BaC03
'I
.
2.
2
'I 2
J.
JI
(
8.
'10.
l1
12.
3
2.5
-22
2
' 1- 2
.33
2
1.5
2
0,67
1.33 0,67
I
t.2
r.5
2
121
211
U.3
0.5
Products
BB
BB+St+Cc+Sc
BB+CC
BB+CC
lllt+st+sc
Bc+Sc
BB+St+Bs
BB+BS
BB+BS
BB+St+Bs
BB+St+Bs
BB+BS
B B b u r b a n k i t e ;S t s t r c n t i a n i t e : C c c a l c i t e ; S c s o d l u m
carbonatehydrate; l'lt |litheritei Bs benstonitei
Bc barytocalci te .
2). The compositions of the synthetic Ba,bearing
burbankite (runs 7-12) are uncertain due to the
presence of other phases. However, the larger
cell parameters and the higher refractive indices
of the Ba-bearing compounds in comparison
with those of the Na,CarSrr(COa)ssuggest that
significant amounts qf Ba must have been incorporated in the structure.
Despite the fact that rare earth elementsmay
be present in natural burbankite up to 0.7 atom
per formula, the results of this experiment suggest that they are not essential for burbankite.
Ifowever, the results are inconclusive on the
Frc. l. Synthetic crystals of NaeCazSrg(CO.)s.
Average length of crystals is approximately
0.03 mm.
BURBANKITE
FROM MONT ST. IIILAIRB
extent of the Ba substitution in burbankite. The
analyses of natural burbankite minerals suggest
that the Ba substitution may be timited as the
Ba content was never found to be greater than
O.5 atom per formula.
AcrNowr,rpcEMENTs
We wish to thank Prof. G. B. Skippen for
his critical reading of the manuscript and Miss
J. Baker for her technical assistance.Lt. Col. Q.
Wight generously provided several specimens of
burbankite for this study. The work is suppofted
by a National Research Council of Canada
grant A5113 to GYC.
REFERENCES
BoRoDD.I,L. S. & KerusnN, Yu. L. (1964): The
first specimen of burbankite found in the USSR.
Dokl. Acad. Jci. UJSR, Earth Sci. Sect. t47,
144-147.
Cruo, G. Y., Henws, D. C., HouNsr,ow, A. W.,
345
MeNoARuyo,J. A. & PERRAULT,G. (1967):
Minerals from the nepheline syenite, Mont SL
Hilaire, Quebec. Can. Mineral. g, 109-123,
Mu,row, C. & Feuev, J. I. (1960): Classificatior
and association of the carbonate minerals of
the Green River Formation. Amer. J. Sci. 258A,
242-246.
Pecone,W. T. & KERR,J. II. (1953): Burbankite
and calkinsite, two new carbonateminerals from
Montana. Amer, Mineral. 38, 1169-1183.
PovlnsNNy:sar,A. S. (1972): Crystal Chemical
Classilication of Minera4*, (translated fmur.
Russian by I. E. S. Bradley). Plenum Press,
New York - London.
Rucrc-mcs,J. C. & Glsrennnn, E. L. (1969): A
computer program for processing electron microprobe analytical data, Dept, Geol. Univ.
Toronto.
VoRoNKov,A. A. & Srrurversr.lve, N. G. (1968):
X-ray diffraction study of the structure of burbankite (Na,Ca)g(Ca,Sr,Ba,Tr)g(COg)s.Soviet
Phystcs-Crystall.L3, 192-196 (Enelish transl.).
Manuscript receivedFebruary 1974.