=Minerals of the eudialyte group from theSagasen larvikite quarry, Porsgrunn,
NorwayAlf Olav Larsen, Arne Asheim and Robert A. Gault
Introduction
Eudialyte, aNa-rich zirconosilicate with varying amounts of Ca, Fe, Mn, REE, Nb, K,Y, Ti, CI and F, was first described from the llimaussaq alkaline complex, SouthGreenland by Stromeyer (1819), Since then, the mineral has been described frommany other alkaline deposits, and is a characteristic mineral in agpaitic nephelinesyenites and their associated pegmatites. In recent years, eudialyte (sensa lata) has
been the subject of extensive studies. The broad compositional variations and new
insight into the crystal chemistry of the mineral group resulted in the definition ofseveral new species by the Eudialyte Nomenclature Subcommittee under theCommission on New Minerals and Mineral Names of the International Mineralogical
Association (Johnsen et al. 2003b).
Brown eudialyte (s. I.) is a common constituent of the agpaitic pegmatites in theLangesundsfjord district in the western part of the Larvik plutonic complex (Br0gger
1890). Recent chemical analyses of the mineral have shown that some localities
contain ferrokentbrooksite (Johnsen et al. 2003a). Other localities hold eudialyte(sensa stricto). Ferrokentbrooksite is the ferrous-iron-dominant analogue ofkentbrooksite with Fe as the predominant element replacing Mn. Kentbrooksite is theMn-REE-Nb-F end member in a solid solution series between eudialyte (s. s.) andferrokentbrooksite, with an extension to oneillite (Johnsen et al. 1998, Johnsen et al.
1999, Johnsen et al. 2003a), as well as to carbokentbrooksite and zirsilite-(Ce)(Khomyakov et al. 2003). Carbokentbrooksite has a significant content of carbonate
and Na > REE for the N4 site, while zirsilite-(Ce) has REE > Na (with Cepredominant) for the N4 site.
In the autumn of 2003 a huge pegmatite dike was uncovered in the Sagasen larvik/te
quarry at M0rje, Porsgrunn. Throughout the winter and spring of 2004, an abundanceof yellow and orange, rarely brown, minerals of the eudialyte group was found.
Because of the conspicuous variation in colour of these eudialyte group minerals, wefelt it would prove interesting to confirm their correct identity. This paper reports thechemical composition and an interpretation of the results in view of the new speciesof the eudialyte group.

Occurrence
The Sagasen larvikite quarry is situated at the southwestern part of the Sagasen hill,at the bottom of the M0rjefjord in Porsgrunn community, Telemark county. The
location is practically the same as the formerly famous Saga I quarry, but lower in thehill-side. The well-known larvikite quarries at Tvedalen are 1-3 km to the south-east,
and in Vestfold county. The pegmatite dike is generally 2.5 m in thickness, with agentle fall (approximately 10°) towards SW. The thickness narrows in the southwestern part of the dike, and eventually pinches out. The dike stretches the wholewidth of the quarry, about 50 m in 2004, but has not yet been completely uncovered
towards the south. The whole of its extent is therefore not known. The pegmatite isterminated towards a tectonic zone in the northern part of the quarry.

58

The pegmatite is mainly composed of from microcline, sodalite, nepheline, biotite,amphibole, aegirine and spreustein (natrolite pseudomorphs after nepheline andsodalite). The major mineral individuals are between 10-50 cm in size. The northernpart of the dike comprises nepheline syenite pegmatite with soda lite practicallyabsent, while the southern part is dominated by large individuals of dark greyish
green sodalite. Leucophanite, astrophyllite and the eudialyte group minerals aremainly confined to the sodalite rich part of the pegmatite. In the northern wall of thequarry, the pegmatite was exposed showing a central core, approximately 50 cm
thick and several metres long, of white saccharoidal albite with abundant dark green
aegirine crystals. Most of the rare minerals are confined to nests located in theinterstices between the main minerals of the pegmatite. Parts of the pegmatite havestrongly suffered hydrothermal alteration, with formation of typical late stage minerals
like f1uorapophyllite, eudidymite, epididymite, behoite, berborite, ancylite-(Ce),parisite-(Ce) and bastnasite-(Ce). Nearly 70 different mineral species are identified
from the pegmatite (Table 1). In addition, a few unknown minerals remain to beidentified.

The eudialyte group minerals
The eudialyte group minerals are among the youngest minerals crystallised during
the magmatic stage of the pegmatite formation. In the Sagiisen pegmatite they occur
as up to fist-size masses filling interstices between feldspar individuals. The massesof eudialyte group minerals generally have an outer rim, varying from a mm to a cm
thick, composed of finely crystalline aegirine, zircon, pyrochlore and fluorite. Theseminerals also occur in veins crisscrossing the masses of eudialyte minerals. Therehas also been observed eudialyte masses, which are completely altered into a
mixture of aegirine, zircon, astrophyllite, pyrochlore and fluorite. Rosenbuschite andtadzhikite have been observed embedded in the eudialyte minerals.
The colours of the eudialyte group minerals in the Sagiisen pegmatite are usually in
different shades of orange and yellow, but transitions to brownish yellow and brownhave been observed. Especially the larger masses may show considerable variationof colours within the same sample.

Chemical composition
Two samples of the eudialyte group minerals showing the most extreme colours(yellow and brown) were chosen for complete chemical analysis. The analyses on
the main and minor elements, except Ti, AI, Fe and the rare earth elements, weredone in wavelength-dispersive mode on a JEOL 733 electron microprobe using thesame analytical conditions and calibration standards as reported in the description offerrokentbrooksite (Johnsen et al. 2003a). Carefully handpicked material wasdecomposed by nitric and sulphuric acids, and the concentrations of Ti, AI and theREE were determined by PerkinElmer Elan ORC-II ICP-MS, while Fe wasdetermined by MS. The amount of CO 2 was determined by LECO CS-200 elementalanalyser. The results are shown in Table 2.
Infrared spectra of the yellow and brown eudialyte group minerals were obtained onground material pressed into a KBr pellet and recorded using a PerkinElmer S-2000
FT-IR spectrometer in the range 4000-450 em". The broad absorption bands atapproximately 3480 and 1640 cm,1 are assigned to the [OH] stretching mode and the[H 2 0] bending mode, respectively. The bands between 1100 and 450 cm,1 are due tothe stretching and bending vibrations in the [SiO.] group. The two bands at 1425 and1506 cm,1 are attributed to the stretching mode of a [C0 3 } group. The spectra aresimilar to each other, except that the bands due to [C0 3] are weaker in the brownsample compared to the yellow sample, reflecting the different concentrations of59

=-=carbonate in the two samples. The infrared spectra are rather similar to that ofxanthopite reported by Larsen et al. (2005), except that the latter mineral has
stronger carbonate bands.

X-ray crystallography
X-ray powder diffraction data on the eudialyte group minerals were obtained using aPhilips X'pert diffractometer (CuKc, radiation, A. = 1.54056 A). Si (NBS 640a) wasused as internal standard. Indexing and least squares refinement were done by theprogram CELREF, and the unit cell dimensions found on the yellow zirsilite-(Ce) area 14.2628(72) A, C 30.0631 (2) A, and V 5296 N.

===Discussion
According to Johnsen et al. (2003b), the general formula of the eudialyte groupminerals is [N(1 )N(2)N(3)N(4)N(5)h[M( 1a)M(1 b)hM(2hM(3)M(4)Z3[Si 24 0 72]0'..x2,
where X = CI, F, OH or C0 3. This large number of separate structural sites gives
theoretically a potential for thousands of different species. At present there are about
twenty species within the eudialyte group. The complexity of the crystal structure
makes it difficult to construct an accurate formula without structural information.
However, a procedure for determining an empirical formula on the basis of chemical
data has been given by Johnsen & Grice (1999). Following this procedure, theyellow eudialyte mineral from Sagasen is zirsilite-(Ce), which is a new species in thelist of minerals from the pegmatites within the Larvik plutonic complex. The brownmineral is ferrokentbrooksite. The empirical formulae are given at the bottom of Table
2. Despite the fact that the two minerals contain significant amounts of carbonate, theEudialyte Nomenclature Subcommittee recommended that the X sites be ignored in
the nomenclature (Johnsen et al. 2003b).

Acknowledgements
We thank E. Austad and A Henriksen for carrying out the CO 2 determinations andthe IR spectrometric analysis, respectively. We are indebted to 1. Engvoldsen, S. ABerge and I. Burvald for information about the minerals in the Sagasen pegmatite.

References
BR0GGER, W. C. (1890): Die Mineralien der Syenitpegmatitgange dersudnorwegischen Augit- und Nephelinsyenite. Zeitschrift fiir Krysta/lographie 16, 1235 + 1-663.
JOHNSEN, O. & GRICE, J. D. (1999): The crystal chemistry of the eudialyte group.
Canadian Mineralogist 37, 865-891.
JOHNSEN, 0., GRICE, J. D. & GAULT, R. A. (1998): Kentbrooksite from theKangerdlugssuaq intrusion, East Greenland, a new Mn-REE-Nb-F end-member in aseries within the eudialyte group: Description and crystal structure. European Journalof Mineralogy 10,207-219.
JOHNSEN, 0., GRICE, J. D. & GAULT, R. A (1999): Oneillite: a new Ca-deficientand REE-rich member of the eudialyte group from Mont Saint-Hilaire, Quebec,Canada. Canadian Mineralogist 37,1295-1301.
JOHNSEN, 0., GRICE, J. D. & GAULT, R. A. (2003a): Ferrokentbrooksite, a newmember of the eudialyte group from Mont Saint-Hilaire, Quebec, Canada. Canadian
Mineralogist 41, 55-60.
JOHNSEN, 0., FERRARIS, G., GAULT, R. A, GRICE, J. D., KAMPF, A R. &PEKOV, I. V. (2003b): The nomenclature of eudialyte-group minerals. Canadian
Mineralogist 41,785-794.
KHOMYAKOV, A. P., DUSMATOV, V. D., FERRARIS, G., GULA, A, IVALDI, G. &NECHELYUSTOV, G. N. (2003): Zirsilite-(Ce),(Na, n )'2( Ce, Na hCa6Mn3Zr3Nb(Si250n)( OH h( C0 3)· H20 and carbokentbrooksite

60

(Na,D),2(Na,CehCa6Mn,lr3Nb(Si,sO?Jl(OHh(C03)'H20, two new eudialyte groupminerals from Dara-i-Pioz alkaline massif, Tajikistan. Zapiski Vserossiyskogo
Mineralogicheskogo Obshvhestva 132 (5), 40-51 (in Russian).
LARSEN, A. 0., ASHEIM, A. & GAULT, R. A. (2005): Ferrokentbrooksite (Bmgger'sxanthopite) from Skutesundskjcer in the Langesundsfjord district, Norway. Norsk
Bergverksmuseum, skrift 30,63-67.
STROMEYER, F. (1819): Summary of meeting 16 December 1819 [Fossilien .... ].
G6ttingische gelehrte Anzeigen 1819 (3), 1993-2000.

Table 1. Minerals identified from the Sagasen pegmatite (Spring 2005).

MineralAbundance

MineralAbundance

aeairine
albiteanalcime
ancvlite-(Ce)arsenopyrite
astrophvllitebastnasite-( Ce)behoiteberboritebiotite (annite)boehmitebritholite-(Ce)calcitecancrinite
carbonat-fluorapatite
cataoleiite
chiavennite
chlorite
epididvmite
eudidvmite
ferrokentbrooksite
fluorapophvllite
fluoritegalenagibbsitegoethitegonnardite
gonverite
hambergite
helvitehematiteheulandite-(Ca)hvdrocerussite
ilmenite

xxxx
xxxx
xxx
xx
xx
xxx
x
x
x
xxxx
xx
x
x
xxx
x
x
x
xx
x
x
xxx
x
xxx
xx
x
x
x
x
x
x
x
xx
x

kentbrooksite
laveniteleucoohanite
Ibllinoite
microcline
molvbdenite
monazite-( Ce)montmorillonite
mosandrite
natroliteneotocite
nepheline
nordstrandite
parisilt-(Ce)pectolite
oolvlithionite
oowellite
ovritepvrochlore
pvrophanite
pyrrhotite
rhodochrosite
rosenbuschitesodalite
sphaleritetadzhikite-(Ce)thomsonite
thoritetritomite-( Ce)tvedalite
wbhlerite
zirconzirsililt-(Ce)

xxxxx
xxxxx
xx
x
x
xxxxx
xx
xxxx
xx
x
xx
x
xxx
xx
x
x
xxxx
xx
x
x
xx
xx
x
xxx
xxx
xxx

xxxx major mineralxxx = subordinant mineral
xx = rarex = very rare61

Table 2. Chemical composition (in oxide weight- %) of zirsilite-(Ce) andferrokentbrooksite from the Sagasen quarry, and corresponding number of atoms per
formula unit based on 29(Si+AI+Zr+Ti+Hf+Nb+Ta).

Si0 2
Ti0 2
Zr02
Hf02
AI 20 3
Y20 3
La203
Ce203
Pr203
Nd 20 3Sm2 0 3EU203
Gd 20 3
Tb 20 3
DY2 0 3
Ho 20 3
Er203
Tm203
Yb 20 3
LU203
Nb20 s
Ta20S
FeO
MnO
MgO
CaO
SrO
Na20
K20
FCI
H2O.
CO 2-O=F-O=CI
Total

Zirsilite-(Ce) (vellow)
24.86743.89 Si
0.200
Ti
0.47
2.881
10.43 Zr
0.078
Hf0.480.114
0.17 AI
0.335Y
1.11
0.499
2.39 La
0.821
3.96 Ce
0.062
0.30 Pr
0.154
0.76 Nd
0.020
0.10 Sm
Eu
0.000
0.01
0.024
0.13 Gd
0.006
0.03 Tb
0.18 Dy
0.033
0.05 Ho
0.009
0.030
0.17 Er
0.005
0.03 Tm
Yb
0038
0.22
0.005
0.03 Lu
0.827
3.23 Nb
0.032
0.21
Ta
1.294
Fe
2.73
3.052
Mn
6.36
Mg
0.000
0.00
4.759
7.84 Ca
0.036
0.11
Sr
11.89710.83 Na
0.152
K
0.21
0.00
F
0.000
0.768
0.80 CI
3.232
0.86
H
0.766
0.99
C
0.00
0.1398.94

Ferrokentbrooksite (brown)
Si25.098
46.03
Si0 2
0.258
0.63 Ti
Ti0 2
2.991
11.25
ZrZr020.056
0.36
HfHf0 2
0.12
AI
0.077
Ab 0 30.218
Y20 3
0.75 Y
La
0.199
0.99
La203
0.263
1.32
Ce
Ce203
0.018
0.09
PrPr203
Nd
0.047
0.24
Nd 20 30.008
0.04 Sm
Sm2 0 3
0.000
0.01
Eu
EU203
0.011
0.06
Gd
Gd 20 30.002
Tb 20 30.01
Tb0.016
0.09
Dy
DY2 0 3
0.003
0.02
Ho
H0 20 3
Er0.015
0.09
Er203
0.002
0.01
Tm
Tm2030.015
0.09Yb
Yb 20 3
Lu
0.002
0.01
LU203
0.503
2.04 Nb
Nb 20 S
0.016
0.11
TaTa20S
2.234
FeO
4.90
Fe
1.575
3.41
Mn
MnO
0.000
Mg
0.00
MgO
5.544
CaO
9.49 Ca
0.054
SrO
0.17 Sr
12.81312.12 Na
Na20
0.285
0.41
K
K20
0.000
0.00
FF
1.072
1.16 CICI
H2O.
2.928
0.81
H
0.357
0.48
C
CO 2
0.00
-O=F
0.26
-O=CI
97.04
Total

• Determined by stoichiometry, calculated assuming 2(OH+CI).
Empirical formula for zirsilite-(Ce) (yellow):(Na, I .90KO.lO!r '2.00(CeO.a2Lao.soNdo.1SPrO.06YbO.04DYo.03Er0.03SmO.02GdO.02Tbo.o,Hoo.o,Tmo.o,Luo.o, YO.33CaO. 10KO.OSSrO.04!r2.>J!Ca4.66Mn,.34)ra.00(Mn '.7' Fe,.29!r3.00( Zr2.aa Hfo.oaTio.06 b.02
(Nb o.a3Ti o ,4Ta003)r ,oo(Si24a7Alol I b4.9aOdO, OH ,(C03)onCI077b.w H20
Empirical formula for ferrokentbrooksite (brown):(Na '2.al CeO.26Lao.20Ndo.osPr0.02DYO.02SmO.O' Gd O.01 Er001 Ybo.o•CaO.34KO.29Y0.22SrO.OS)r'4.30(Cas.20Mno.ao)ra.oo(Fe2.23Mno.77b.oo(Zr2.99Hfo.06b.os( Nbo.soTio.26Sio.laTaO.02)r0.96(Si24.92AlooabsooOdO, OH, (C03)0.36C1'07boo' H2062