AmericanMineralogist,Volume71,pages1028-1033,1986
Kimuraite, CaYr(CO)4.6H2O, a new mineral from fissuresin an alkali
olivine basalt from Saga Prefecture,Japan, and new data on lokkaite
Kozo N,rc,rsHrMAr* Rrrsuno MtylwlrIo
JuNxo Tlxl,sn, lzuvtt Nlrar
Departmentof Chemistry,University of Tsukuba,Ibaraki 305,Japan
KrN-rcrrr Slxunll
l-15 KandaSuda-cho,
Chiyoda,Tokyo l0l, Japan
Axrnl Klro
Slrosnr Mlrsunlru,,
Museum,Tokyo 160,Japan
Departmentof Geology,NationalScience
Snorcnrno lw,llo
Fukuoka811-31,Japan
l64l-5 Kubo,Koga-cho,
Kasuya-gun,
Ansrru,cr
Kimuraite, ideally CaYr(CO3)4'6HrO,occursas a fissuremineral in alkali basalt exposed
at Kirigo, Hizen-cho, Higashi Matsuura-gun, SagaPrefecture,Japan, and vicinity, in association with lokkaite-(Y) and lanthanite-(Nd). It is orthorhombic, space group Imm2,
Immm, 1222,or 12,2,2,;a:9.2545(8), b:23.976(4), c : 6.0433(7)lr, V:1340.9(3)
At,7:4.
Kimuraite is light purplish to pinkish white with a vitreous to silky luster. The
hardness(Mohs) is2t/z on {010}, the density is 2.98 g/cm3 (calc.), and there is a perfect
cleavageon {010}. Optically it is biaxial negative,2V:70(5), r < v, weak. Refractive
i n d i c e s a r e a: 1 . 5 8 4 ( 2 ) , 0 : 1 . 6 1 2 ( 2 ) , t : 1 . 6 2 6 ( 2 ) ; u : X , b : I , a n d c : Z . T h e s t r o n g e s t
12.06(100X020),6.02(40X040),
lines in the X-ray powder pattern are ld (I/I)(hKl)l
2.93(10)(25r,022),
4.01(20X060),
3.76(30X051),
r), 4.87(10X031),
4.64(10X200),
5.93(20X01
2.05(l2X0.l l.l). Completechemicalanalysisof the associatedlokkaite gavea new chemical formula, CaY4(CO3)?.
9HrO.
Iurnooucrrox
OccunnnNcB
In 1982 one ofthe authors (S.I.) collected a few fragile
fissureminerals in alkali olivine basalt exposedat Kirigo,
Hizen-cho, Higashi Matsuura-gun, Saga Prefecture, Japan, and sent them to K.S. for identification. The latter
recognizedtheir unusualnature, i.e., solubility in acid with
effervescenceand fluorescenceunder ultraviolet light. Preliminary chemical analysesand X-ray powder studies by
S.M. and A.K. showed them to be lanthanite, lokkaite,
and a new hydrous carbonate ofY-group rare-earth elements and Ca. The authors'combined studies suggested
that a simple hydration oflokkaite results in the formation
of the assemblageof lanthanite and the previously undescribedmineral.
This new mineral has been named kimuraite in honor
of Dr. Kenjiro Kimura (1896- ), Emeritus Professorat
the University of Tokyo, in recognition of his outstanding
contributions to the geochemistryand mineral chemistry
of rare-earthminerals. The mineral and name have been
approved by the Commission on New Minerals and Mineral Names, IMA. Type material has been preserved at
National ScienceMuseum. Tokvo and Sakurai Museum.
Tokyo.
* Deceased
on January6, 1985.
0003404X/86/0708-l
028$02.00
The locality is an exposure of alkali olivine basalt of
the first-stagetrachybasaltin the Higashi Matsuura District (Aoki, 1959), which unconformably overlies early
Pleistocene sedimentary rocks and pre-Tertiary granodiorite. The basalt is a lava flow with nearly horizontal
flowagestructures.The new mineral occurs in the upper
horizon of the flow. The exposuresof kimuraite-bearing
basalt are distributed over 5 km around the first locality.
The basalt has a gray homogeneousgroundmasswith olive-greenolivine phenocrystsreaching 2 mm across.The
rare-earth-elementcarbonates are exclusively found in
minor fissuresdeveloped nearly parallel to the flowage
structure. The fissuresare of various sizes up to l0 cm
long and 5 mm wide.
Kimuraite occurs as spherulitic aggegatesof scales4
cm long and 2 cm wide. It is closely associatedwith coarsergrainedlanthanite, which commonly has rectangularoutlines up to 2 mm on an edge.These two minerals are in
most casesunderlain by lokkaite, which forms snow-white
spherulitic aggregateson fissure walls. There are also mineral-free and calcite- and/or aragonite-bearing fissures
without rare-earth-elementcarbonates.In addition to the
fissures,tiny druses including olivine grains are developed. The fissureswith rare-earth-elementcarbonateshave
no alteration haloes around them.
I 028
rQ29
NAGASHIMA ET AL.: zuMURAITE
Table l.
Chemicalanalvsisof kimuraite
wt?
0.50
0.018
Ce2O3
0.02
0.001
Pr203
0.37
0.0'15
Nd2o3
2.97
0.107
"u2o3
Fig. l. srr"rphotographof kimuraite.Scalebar is 100pm.
s^2o3
0.95
0..033
Eu203
0.39
0,013
cd2o3
2.49
0.083
Tb2O3
0.36
0.012
Dy^O.
2,44
0.079
Ho2O3
0.62
0.020
Er2O3
1, 6 9
0.053
Tm2O3
0.17
0.005
Ybio3
0.56
0,017
Lu2O3
0.06
0.002
Y, o.
(rRE2O3
Oprrcnr, AND PHYSTCALpRopERTrEs
Kirnuraite is light purplish to pinkish white in color,
reflectingthe presenceof rare-earth elementssuch as Nd.
The luster is vitreous to silky on the cleavageplane. The
hardnessmeasuredon the cleavageplane, which is perfect
along {010}, is 2t/2.The calculateddensity is 2.98 g/cm3,
which is appreciably higher than the measured density,
2.6(l) g/cm] . The diflerenceis ascribedto the porous state
of the mineral. The senrphotograph (Fig. l) indicatesthat
the cluster of kimuraite is a loose aggregateof tabular
crystals.It is optically biaxial and negative;2Y: 70(5);
dispersion r < % weak. The refractive indices, measured
by the immersionmethod, areq: 1.584(2),B : 1.612(2),
t : 1.626(2).The optical orientation is a : X b : I, and
c: Z. It is strongly fluorescent under short- and longwave ultraviolet light, showing reddish purple and purple
colors,respectively.Itis readily sofublewith effervescence
in dilute hydrochloric acid.
CrrnMrc.tI, coMposrrroN
Kimuraite was chemically analyzedwith an Inductively
Coupled Plasma-Atomic Emission Spectrometer(rcr-ars).
Water and CO, weredeterminedby corrventionalanalysis.
In the preparation of standard solutions for the rcp-AEs
analysis, special care was taken to preyent spectral interferences(Iwasaki, Fuwa, and Haraguchi, ms.). In order to
minimize the variation of the nebulization efficiencyowing to the differenceofthe viscositiesofthe solutions, the
acid contents in each standard solution were adjusted to
1.2 NHCI to match the digestedsample solution. A 6.55mg sample was dissolved in 40 mL of 1.2 N HCl. The
measurementswere repeatedthree times for eachelement.
The data were then averagedand corrected for the spectral
interferences.The results of chemical analysesgiven in
Table I yield the empirical formula Ca.-nnREEr.orCr
rnO,r.
6.12H2O, calculated on the basis of O : 12 for the anhydrous part. This leadsto the ideal formula CaYr(COr)o.
6HrO with Z: 4, wtrere Y signifies the dominance of
No. atoms
( o=12 )
2 9, 4 1
1.57
43.00
2.O2 |
CaO
9.23
coz
29,13.
H20
18.32
Total-
9 9. 6 8
0.99
12.24
Number of atoms is basedon 12 oxygenatoms
in the anhydrous part.
Y-group rare-earth elements. If specification of rare-earth
elements is needed, the mineral should be termed kimuraite-(Y;.
Kimuraite has an unusual distribution pattern of lanthanides (Fig. 2), in which Ce is anomalouslypoorer than
both La and Pr, as compared to the Oddo-Harkins' rule
(Oddo, 1914; Harkins, 1917).Furthermore,the low-Ce
anomaly was observed in the chemical composition ofthe
associatedlanthanite-(Nd) (Table 2,Fig.3). A similar Ce
anomaly was reported from Brazil (Cesbron et al., 1979;
Roberts et al., 1980) for lanthanite-(Nd) formed in a sedimentary environment.
I
o
o
z
ta Ceft |tt|dPrnSntuGdIb Dytlo Er TmYbLu
Fig. 2. Distribution pattern of lanthanides in kimuraite, indicating a Ce anomaly.
1030
NAGASHIMA ET AL.: KIMURAITE
I
o)
tl
q
tr
E
c
z
F
LaCePr lrldPrnSrnEuGd
Tb DyHoEr TmYbLu
Fig. 3. Distribution pattern of lanthanidesin lanthanite-(Nd).
Ce is less abundant than La and Pr.
X-nc.y CRYSTALLoGRAPHY
X-ray single-crystal study including Weissenberg,
precession,and four-circle diftactometer methods showed
kimuraite to be orthorhombic. The diffraction patterns
indicate the spacegroup to be Imm2, Immm, 1222, or
122,2t. A least-squarestechnique applied to the diffraction anglesof 25 strong reflections in the range of 40' <
20 < 50 measured by an automated four-circle diffractometer produced the refined cell parameters 4 :
9.2545(8),
b : 23.976(4),
c: 6.0433(7)A, V : 1340.9(3)
43.
X-ray powder data (Table 3) were obtained using an
X-ray powder difractometer, Ni-filtered CuKa radiation,
a scanrate of Wlmin, and Si (NBS, SRM640a) and mica
(NBS, SRM675) as internal standards.A preferred ori-
Table 2. Chemicalanalysisof lanthanite-(Nd)from
Hizen-cho,SagaPrefecture,Japan
wtA
Lu2o3
No.
atons
(o=9)
15.71
'l
.11
0.596
C e 2O 3
--2-3
5.18
0.193
Ndzo3
2 3. 4 2
0.856
Sm-O-
3.69
0.130
Eu2O3
0.80
0.028
Gdzo3
1.14
0.059
Tb2o3
0.10
0.003
Dv^o^
0.34
0.011
Ho2O3
0.02
0.001
Er2O
0.03
0 . 00'1
Yb2o3
n.d.
Lu2O3
n.d.
3
Tn2O3
Y-O(tRE2O3
0.48
0.042
o.026
52.68
1.9461
C02
2 1. 3 8
3.04
Hzo
2 3. 3 7
15.95
Total
9 7. 4 3
4000
Fig. 4.
1000
2000
wave number ( cm-1)
Infrared
absorption
400
spectrum of kimuraite.
entation effect due to the perfect {010} cleavagemay be
present.
INrn-l,nnt spEcrRA AND THERMAL BEHAvTOR
An infrared absorption spectrum (Fig. a) was obtained
with a Hrracru 260-50 infrared spectrophotometerusing
the KBr method. The presenceof water moleculesin kimuraite is shown by the broad band of HrO stretching
vibrations in the frequency range 3500-3000 cm-' and
by the HrO deformation band, which appearsas a shoulder at 1630 cm-'. The broad bands in the region 1500I 400 cm- r, weakabsorptionsat I 090 and I 062 cm-', and
medium onesat 856,842,748,and 685 cm-1 are attributed to the CO3- absorption bands.
The pra and TcA curves are given in Figure 5. The
former has a strong endothermic peak at l60oC, corresponding to the loss ofwater. There are apparently four
small endothermicpeaksin the rangeof 500-750'C, which
are interpreted to representthe loss of COr. The weightloss steps on a synchronized-recordingrcA curye correspond well with the endothermic changesin the ora diagram. The rce diagram shows two steps of the weight
loss.One in the rangeof60-400"C colrespondsto the loss
ofwater, and the other, in the range of400-750'C to the
loss of COr. This is consistent with the results of the
chemical analysis.
The infrared spectra of kimuraite after thermal treatment (Fig. 6) confirm the interpretation of the results of
the orn and rcn studies. The infrared spectrum of the
sample heated at 300'C has no HrO absorption, and the
spectrumofthe sampleheatedat 550"Cshowsa significant
decreasein the intensities of the CO3- absorptions. The
sample heated at 1000'C gives the absorption peaks of
rare-earthoxides. The weak CO3- absorption band in the
range of 1600-1400 cm-' is due to CaCOr, which was
formed by the carbonation of CaO.
Nnw olu
oN LoKKATTE
Lokkaite was originally reported as tengerite by Vorma
et al. (1966) from the Py6rdnmaa pegmatiteat Kangasala
in southwesternFinland. The mineral occurs as isolated
white radial disclike aggregateson the surfaces ofand in
fissuresin albite. Later, it was showr to be a new mineral
103r
NAGASHIMA ET AL.: KIMURAITE
Table 3. X-ray powder-diffraction data for kimuraite
))
h k't.
a
_caIc.
s_ o b s .
r/ra
hkL
2
1
4
1
0
1 1. 9 9
5.99
5. 86
5.06
12.06
8.66
6.02
5.93
5.11
100
2
40
20
1
41
1
312
2100
o a 2
431
2,15
2.15
2.13
z.i3
2.09
3
0
2
6
4
4.82
4.63
4.32
4.00
4 .8'7
4.64
4.33
4.0'l
10
10
3
20
5
0
3
0
4
4
111
8 1
1 3
6 0
51
30
1
6
7
6
0
2
0
2
0
3 3
I 2
102
111
5 3
3.'16
3.66
3.63
4
1
3
6
6
0
8
2
5
3.02
3-O2
3.00
2.93
2.92
2
8
0
I
1
2.64
1
|
8
|
|
10
2.69
5
5
8
2.52 |
2.51 |
6
2
9
6
10
4
2.48
2.44
2.41
2.40
2
2
2
2
0
2
'l
2.31
2.21
2.20
2.16 \
2-16 |
2.32
2.27
2.23
1
1
1
2.16
4 sh
: shoulaler,
br
4 0
4 8
4 2
5 0
1 6
013
4 sh
3.01
2.55
4
9
sh
3.68
3.64
3. 35
3.16
.48
.44
.42
.41
6
1
2
0
2
1
3
1
oDs
|
1
t
|
2. 15
4sh
2.13
8
2,09
7
2.05
2.03
2.0',1t
2.00 j
2.05
2.02
zbt
2.01
br
1.9',70
1,972
br
1.953
1.933
1. 8 7 8
1.875
1.857
1.948
1.934
1.881
1.876
1.858
br
1.837
1.831
1.816
1.'770
1.7661
1.'7641
1.836
1.832
'I
.818
1.173
sh
b!
sh
5 2 1
2 102
0 7 3
2 ' 1 31
0151
1.'751
1.7401
1.1361
1.648
1.545
1.648
1 .54'7
br
br
16 0
3 1
3 4
151
4 4
1.498
1.469
1.4661
r.4661
1.4651
1.502
1.469
br
br
1.374
1,349
1.376
1 -343
0
6
i
2
0
3
carc.
6 0 2
0 8 4
1.754
1 , ' 74 1
br
br
: broaal.
with the chemicalformula CaorrREE, ,r(CO, ,r), . I .58HrO
and named lokkaite by Perttunen (1971). Although he
mentioned that the essentialdiference between lokkaite
and tengeriteis not in the degreeofhydration, significant
contamination of his samplesby tengerite precluded an
adequateanalysis of lokkaite. Since pure specimensare
available from the Japaneselocality, we have carried out
an X-ray powder study and a complete chemical analysis
of this mineral.
X-ray powder data for lokkaite using Si and mica in-
ternal standards are given in Table 4. The original data
for lokkaite from the Pyiirdnmaa pegmatite are included
for comparisonand to prove the identity of the two phases.
The refined unit-cell dimensions, produced by the pro-
I
a
o
a
@
o
a
G
F
'
R.T
200
400
600
800
1000
Temperature('C )
Fig. 5.
ora and rcA curves ofkimuraite
pressure.
under atmospheric
4000
2000
1000
Wave number (cm-r )
Fig. 6. Infrared absorption
550. and 1000f.
spectra ofheated kimuraite
400
at 300,
ro32
NAGASHIMA ET AL.: KIMURAITE
Table 4. X-ray powder-diftaction data for lokkaites
Present
hkx
d
carc.
study
d.
obs.
Pelttunen
r/ro
(1971)
Table 5. Chemical analyses oflokkaite from SagaPrefecture,
Japan, and Kangasala, southwestern Finland
Presenu
I
wtt
200
400
600
210
410
19.67
9, 8 4
6.56
5.83
5.19
19.8'1
9.90
6.56
5.85
5.19
2,06
't.9't1
2.06
40
1.979
1.9'13
1.882
10
1 80 2
162 0
830
1.915
r.880
,
o<
cu2o3
0.43
0.029
o,7
Pt2 o3
0.51
0.04'1
0.6- 1.',1
0.2- 0.4
Nd2o3
7. 1 3
sm2O3
3.84
' t. 1 2
0.398
0.241
1.1- 1.8
1.6- 2,2
0. 107
0.452
4.1- 5.4
6
2.46
2.41
o(
0,2
6
3.43
2.46
2.41
,
0.2- 0.3
10
50
100
7
10
7
10
40
3.04
2.947
2.93'l
30
25
2.443
20
30
40
2 .1 5 8
2.045
1.904
1. 8 7 0
Mean
0.022
75
10
60
100
20
3.45
3.23
3.06
3.0't
(19?1)
Range of
0.33
4.59
4. 4 3
3.90
3.81
3.60
3.45
3.22
3.05
3.00
atoms
Lu203
5,79
412
612
020
1 00 2
812
No.
35
50
55
70
5 'l0
4.63
4.4'1
3.93
3 .8 3
022
1 60 0
1 02 0
160 2
1 8 ' 10
4.62
4.49
3.94
3.84
19.6
9.1'7
002
610
' 1 00 0
810
212
Perttunen
stualy
oDs.
10
( O=21 )
Eo2o
3
7.41
't.22
Gd
2o3
Tb2o3
0.073
0.354
0 .0 6 5
results{g)
1.1- 1.5
6.2- 8.8
value
0.3
' ,.l3
1.8
4.6
1.2
6.8
t!ace
Dv-o^
6.02
Ho
2o3
Et2o3
1. 1 2
2.35
0 . ' ,315
3.1- 4.4
T'2 o3
0.28
0.016
0 . 7 - 1. 2
4.0
0.9
vb2o3
0.80
0.045
1.8- 3.0
2.2
Lu2O3
0.10
20,64
0.005
-29.5
29.0
54.06
3.99
Yzo3
(xRE2O3
2.005
trace
29
53.0
)
CaO
gram of Appleman and Evans (1973), are a: 39.35(2),
b -- 6.104(4), and c : 9.26(l) A, which are comparable
to those of the original material, a : 39.07, b : 6.079,
a n d c : 9 . 1 9A .
Chemical analysisof Japaneselokkaite was carried out
applying the sameproceduresas for kimuraite (Table 5).
The empirical formula, calculatedon the basis of O : 2l
in the anhydrouspart, is Ca,.orREEr.eeC,
ooo2,.8.6HrO,or
ideally CaY.(COr),.9HrO. Ca is an essentialcomponent
oflokkaite. This distinguisheslokkaite from tengerite.The
empirical formula of the original lokkaite is Ca".r, REE, sr. 3.85HrO on the
(COrrr)r' l. 58HrO or Cao'6REE38sC7
32O2r
presentbasis.Perttunen (1971) mentioned that the X-ray
powder pattern of his specimen showed overlapping of
tengeriteand lokkaite reflections(Table 4). The chemical
analysis of cations was therefore made with the electron
microprobe (Vorma eIal.,1966), but this doesnot appear
to be suitable for the analysis of a hydrous carbonate
mineral. The infrared absorption spectrum of Japanese
lokkaite is given in Figure 7. It is worth noting that the
infrared spectraof lokkaite and kimuraite resembleeach
other, suggestinga close structural relationship between
the two minerals.
I
o
2a.09
c02
H 2 O{ - l
0.3- 0.4
n.d.
Fe2O3
lra.i:
H2O(+)
I
TOIAI
10 1 . 5 3
RrrarroNsHrPs
7.00
i'i.2o
0.4
3 2. 4
5,4
1.6
9 6. 0
ro orHER MTNERALS
Kimuraite is the second mineral in the CaO-REErO3COr-HrO system,lokkaite being the first. The two minerals show a marked structural resemblance.The cell parametersa and c of kimuraite, 9.2545(8)and 6.0433(7)
A, arevery closeto c and Doflokkaite, 9.26(l) and 6.104(4)
A, respectively.The ratio of cation numbers in kimuraite
and lokkaite, 3:5, correspondsto that of the D dimension
of kimuraite and a of Japaneselokkaite, i.e., 23.976:
39.35 : 3;4.92 * 3:5. In addition, the ratio 3:5 is equal
to that of the total oxygen atoms in both minerals, suggestingsimilar packingof the structural constituents.Perttunen (1971) mentioned that lokkaite has a distinct superstructure,the dimensions of the subcellbeinga' : t/za,
b' : b, and c' : c. This was also confirmed in the powder
pattern ofJapaneselokkaite (Table 4). On the other hand,
kimuraite does not show such a feature. This evidence
indicates that the structural relationship between the two
minerals is not so simple. In order to solve the problem,
crystal-structureanalysesof the two minerals are being
performed by the secondauthor.
An interestingcompositional relationship is also found
in the mineral assemblagefrom Kirigo and the neighboring exposures.This is expressedby the equation
t:
4000
2000
1000
Wavenumber (cm-l)
400
Fig.7. Infrared absorption spectrum of lokkaite. A marked
resemblance to the spectrum of kimuraite is observed.
CaREE(COr)?'gHrO+ 5HrO
lokkaite
- REEr(COr)3.8HrO+ CaREET(CO3)4.6HrO.
kimuraite
lanthanite
NAGASHIMA ET AL.: KIMURAITE
This equation accounts for the formation of the lanthanite-kimuraite assemblage by simple hydration of lokkaite, except for the minor discrepancy in the distribution
patterns of lanthanides of these minerals.
AcxNowr,nocMENTS
The rcp-e,esanalytical data were collected at Fuwa Laboratory,
Department of Chemistry, Faculty of Science,University of Tokyo. The authors are grateful to Professor Keiichiro Fuwa, Dr.
Hiroki Haraguchi, and Dr. Kiyoshi Iwasaki for their valuable
advice concerningthe rcr-lrs analysis.The authors thank lkuo
Iida, Chemical Analysis Center, University of Tsukuba, for the
organic elementary analysis.
RrrnnnNcns
Aoki, Ken-ichiro. (1959) Petrology ofalkali rocks ofthe lki Islands and Higashi-matsuuraDistrict, Japan. Tohoku University ScienceReports, 3rd series,6, (2) 261-310.
Appleman,D.8., and Evans,H.T., Jr. (1973)Job 9214:Indexing
and least-squaresrefinement ofpowder diffraction data. National Technical Information Service, U.S. Depanment of
Commerce,Springfield,Virginia, Document PB-216, 188.
r033
Cesbron, Fabien, Sichdre,M.-C., Vachey, H6ldne, Cassedanne,
J.-P., and Cassedanne,J.-O. (1979) La lanthanite i europium
de Curitiba, Paran6,Br6sil. Bulletin de Min6ralogie, 102,342347.
Harkins, W.D. (1917) The evolution of the elements and the
stability of complex atoms. American Chemical SocietyJournal,39, 856-879.
Oddo, Giuseppe.(1914) Die Molekularstruktur der radioaktiven
Atome. Zeitschrift fiir Anorganische und Allgemeine Chemie,
87,253-268.
Perttunen, Vesa. (1971) Lokkaite, a new hydrous RE-carbonate
from Pydriinmaa pegmatite in Kangasala, SW-Finland. Geological Society of Finland Bulletin, 43,6'l-72.
Roberts, A.C., Chao, G.Y., and Cesbron, Fabien. (1980) Lanthanite-(Nd), a new mineral from Curitiba, Paran6, Brazll
GeologicalSurvey ofCanada, 80-lC, l4I-145.
Vorma, Atso, Ojanperii, Pentti, Hoffrdn, Viiinii, Siivola, Jaakko,
and Ltifgen, Arvo. (1966) Rare earth minerals from the Pyiirdnmaa pegmatite in Kangasala, southeastern Finland. Bulletin Commission G6ologiquede Finlande, 38,241-274.
Maxuscnrpr REcETVED
SnprBrvrsrn5, 1985
MlNuscnrpr AccEprEDMencH 18. 1986