uedaite-(ce), a new member of the epidote group with mn at the a site, from shodoshima, kagawa...

Eur. J. Mineral.2008, 20, 261–269Published online February 2008

Uedaite-(Ce), a new member of the epidote group with Mn at the A site,from Shodoshima, Kagawa Prefecture, Japan

RitsuroMIYAWAKI1,*, Kazumi YOKOYAMA1, SatoshiMATSUBARA1, Yukiyasu TSUTSUMI1

and Atsushi GOTO2

1 Department of Geology, National Museum of Nature and Science, 3-23-1, Hyakunin-cho, Shinjuku,Tokyo 169-0073, Japan

*Corresponding author, e-mail: [email protected] School of Science, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2201, Japan

Abstract: Uedaite-(Ce), ideally Mn2+CeAl2Fe(Si2O7)(SiO4)O(OH), occurs in granite at Shodoshima Island in Seto In-land sea, Kagawa Prefecture, Japan. It is monoclinic, P21/m, a = 8.939(8) Å, b = 5.742(4) Å, c = 10.187(8)Å, β = 115.10(6)◦, V = 473.5(6) Å3, Z = 2. The four strongest lines in the powder XRD pattern [d(Å), I/I0,hkl] are (2.92, 100, −302); (3.53, 54, −211); (2.71, 43, 013 120 300) and (2.62, 39, −311). Electron microprobeanalysis gave (wt.%); SiO2 29.94, Al2O3 16.02, FeO 16.01, MnO 6.01, MgO 0.07, CaO 2.42, La2O3 3.09, Ce2O3

10.75, Pr2O3 1.83, Nd2O3 6.44, Sm2O3 1.35, Gd2O3 0.54, Y2O3 0.72, ThO2 0.51, and lead to the empirical formulaMn0.51Ca0.26Ce0.39Nd0.23La0.11Pr0.07Sm0.05Y0.04Gd0.02Th0.01Al1.89Fe1.34Mg0.01(Si2O7)(SiO4)O0.85(OH) on the basis of 3 siliconand 1 hydrogen atoms per formula unit. The estimated content of H2O is 1.50 and the total is 97.20. The variation in con-centration of Mn in uedaite-(Ce) and associated allanite-(Ce) showed negative linear correlation with that of Ca, suggest-ing isomorphous substitution of Mn for Ca. The crystal structure of uedaite-(Ce) was refined to wR1 = 0.0337 with single-crystal X-ray diffraction data. The refinement of occupancy parameters for the A and M sites yielded the structural formulaA1(Mn0.650Ca0.350)A2(Ce0.914Fe0.086)M1(Al0.873Fe0.127)M2(Al0.988Fe0.012)M3(Fe0.875Al0.125)(Si2O7)(SiO4)O(OH), and confirmed thereplacement of Ca with Mn at the A site. Uedaite-(Ce) is a Mn2+-analogue of allanite-(Ce). The calculated density of uedaite-(Ce) is 4.19 g/cm3. Uedaite-(Ce) occurs as short prismatic crystals less than 1 mm length. Crystals are black to dark brown incolor. Uedaite-(Ce) is associated with allanite-(Ce), monazite-(Ce), zircon and thorite, and is often altered to bastnäsite-(Ce). Thenew mineral is biaxial negative and transparent with pleochroism from brown to yellow. However, optical properties are too similarto those of allanite-(Ce), thus distinction by crystal optics is not possible.

Key-words: uedaite, new mineral, crystal structure, Shodoshima, epidote group, allanite, manganese, REE.

Introduction

A Mn-rich mineral in the epidote group was recognizedwith allanite-(Ce), monazite-(Ce), zircon and thorite in asample of heavy minerals separated from a granite for agedetermination. The granite is from Shodoshima Island, Ka-gawa Prefecture, Japan, which is famous for the localityof granite used as huge boulders in the foundation stone-wall of Osaka Castle built in the 17th Century. Single-crystal structure determination and a total of more than100 electron microprobe analyses of the Mn-rich mineraland allanite-(Ce) from the locality revealed that the mineralis a new member of the epidote group with Mn replacingCa at the A site.

The mineral and mineral name were approved by theInternational Mineralogical Association, Commission onNew Minerals, Nomenclature and Classification, #2006-022. The mineral is named according to the recently ap-proved nomenclature scheme for epidote-group minerals

(Armbruster et al., 2006), and after the late Prof. TateoUeda (1912–2000), who was the first to solve the crys-tal structure of allanite (Ueda, 1955). Type material is de-posited in the National Museum of Nature and Science,Japan, under the registration number NSM-M28864.

Geological background and occurrence mode

The new mineral, uedaite-(Ce), was found in a granite ata quarry in Shodoshima Island, Kagawa Prefecture, west-ern Japan (N 34◦33′ E 134◦20′). The granite is Creta-ceous in age, intruding into the Ryoke metamorphic belt.Both granite and metamorphic rocks comprise the base-ment of the island and were widely covered by Miocenevolcanoclastic sediments (Fig. 1). In the quarry, a few me-ters wide Miocene dykes of basalt and andesite are cross-cutting the granite body. Most granites on the island contain

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262 R. Miyawaki, K. Yokoyama, S. Matsubara, Y. Tsutsumi, A. Goto

Fig. 1. A geological framework of the Shodoshima Island (afterKutsukake et al., 1979) with an indication of the type locality ofuedaite-(Ce).

allanite (Kutsukake et al., 1979). Uedaite-(Ce) was foundwith allanite-(Ce), at first, from the heavy mineral fractionseparated from the granite for age determination of mon-azite and thorite.

The granite is coarse-grained and equigranular, consist-ing mainly of quartz, plagioclase, K-feldspar and biotitewith minor amounts of garnet, monazite and zircon. Biotiteis strongly altered to chlorite. Uedaite-(Ce) and thorite oc-cur in trace concentrations.

Appearance, physical and optical properties

Uedaite-(Ce) occurs as short-prismatic crystals elongatedalong the b axis and less than 1 mm in length. It isoften altered to bastnäsite-(Ce) (Fig. 2). The a:b:c ratiocalculated from the single-crystal unit-cell parameters is1.5506:1:1.7597. Uedaite-(Ce) is translucent to opaque,and is black to dark brown in color with grey streak andvitreous luster. Pleochroism is brown to yellow. Orienta-tion: Y = b. No fluorescence was observed under eithershort- or long-wave UV light. Uedaite-(Ce) is optically bi-axial negative with β (=Y) 1.770(5) (589 nm). X and Zcould not be determined because of the tiny, platy fragmentavailable. 2V (meas.) = large. The hardness in Mohs’ scaleis 5–6. It is brittle with uneven fracture. Cleavage is pooron {001}. Density could not be measured because of inter-growth with other minerals (Fig. 2). The calculated densityis 4.19 g/cm3 based on the empirical formula and single-crystal data.

Chemical composition

Chemical analyses were carried out for uedaite-(Ce) andallanite-(Ce) using a JEOL JXA-8800M WDS electron

Table 1. Chemical composition of uedaite-(Ce).

Constituent Wt.% Range Probe standardSiO2 29.94(15) 29.75–30.10 wollastoniteAl2O3 16.02(16) 15.78–16.24 sillimaniteFeO 16.01(24) 15.60–16.21 Fe2SiO4

MnO 6.01(14) 5.86–6.16 rhodoniteMgO 0.07(1) 0.06–0.08 Mg2SiO4

CaO 2.42(16) 2.25–2.61 wollastoniteLa2O3 3.09(61) 2.13–3.56 LaP5O14

Ce2O3 10.75(112) 8.88–11.57 CeP5O14

Pr2O3 1.83(11) 1.67–1.98 PrP5O14

Nd2O3 6.44(25) 6.12–6.83 NdP5O14

Sm2O3 1.35(44) 1.05–2.13 SmP5O14

Gd2O3 0.54(46) 0.24–1.32 GdP5O14

Y2O3 0.72(51) 0.35–1.62 YP5O14

ThO2 0.51(15) 0.31–0.66 ThO2

H2O 1.50 calculatedTotal 97.20

microprobe analyzer (15kV, 20 nA, and 2 μm beamdiameter). Fluorine was sought for, but not detected. Theamount of H2O was calculated by stoichiometry fromthe results of the crystal-structure analysis, based on 3 Siapfu and 1 (OH). The analytical result for uedaite-(Ce)is given in Table 1 with analytical standard materials.The standard deviations of the 5 analyses are given inparentheses following averages. The low totals of theanalysis of uedaite-(Ce) (Table 1) may derive from theestimation of oxidation state of Fe as being divalent andthe lack of determination of the trace amounts of minorlanthanides, i.e., Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu, withconcentrations under the detection limits for the quantita-tive analyses. The empirical formula based on 3 Si apfuis: Mn0.51Ca0.26Ce0.39Nd0.23La0.11Pr0.07Sm0.05Y0.04Gd0.02Th0.01Al1.89Fe1.34Mg0.01(Si2O7)(SiO4)O0.85(OH). Accord-ing to the recommended nomenclature of epidote-groupminerals (Armbruster et al., 2006), the empirical formulacan be expressed on the basis of Σ(A + M + T ) = 8as: Mn0.51Ca0.26Ce0.40Nd0.23La0.12Pr0.07Sm0.05Y0.04Gd0.02Th0.01Al1.91Fe1.35Mg0.01Si3.02O11.85(OH). Thus the Si <3.05 apfu criterion is fulfilled indicating that A site vacan-cies or incomplete A site cation analyses need not to beconsidered.

The simplified formula is (Mn, Ca, Fe)(Ce, Nd, Fe)(Al,Fe)2(Fe, Al)(Si2O7)(SiO4)O(OH). The ideal formula ofend-member is: Mn2+CeAl2Fe2+(Si2O7)(SiO4)O(OH),which requires: MnO 11.86, FeO 12.01, Al2O3 17.07,Ce2O3 27.44, SiO2 30.13, H2O 1.51, total 100 wt.%.

Several granite samples were collected from the samequarry to study compositional variation of uedaite-(Ce)and allanite-(Ce). A total of more than 100 analyses of 25grains of uedaite-(Ce) and allanite-(Ce) were carried outwith the electron-microprobe analyzer. Individual grainsshowed no apparent zonation in chemistry, suggesting theirhomogeneity. However, the Mn content in the mineralsvaries from grain to grain. The wide compositional varia-tion for Mn and Ca indicates a continuous solid solution be-tween uedaite-(Ce) and allanite-(Ce). Two trends of nega-tive linear correlation with Ca could be observed for the Mn

Uedaite-(Ce), a new member of the epidote group 263

Fig. 2. Microphotographs of uedaite-(Ce). A: photomicrograph of a grain of uedaite-(Ce) on a fracture surface. It is partly altered intobastnäsite-(Ce). B: photomicrograph plane-polarized light (PPL) of another grain of uedaite-(Ce). C: back-scattered electron image (BEI) ofthe same grain shown in B. D: back-scattered electron image (BEI) of another grain of uedaite-(Ce). It is strongly replaced by bastnäsite-(Ce)as an altered product. Abbreviations: ued = uedaite-(Ce), bas = bastnäsite-(Ce), chl = chlorite, mon = monazite-(Ce).

variation in uedaite-(Ce) and allanite-(Ce) solid solution(Fig. 3). The most remarkable one among them has a gra-dient of –1 suggesting the substitution of Mn for Ca at theA sites in this mineral. Some allanite-(Ce) grains plot apartfrom the linear trend mentioned above (Fig. 3), indicatingfurther substitutions of Mn for Al, Fe and others in the oc-tahedral M sites.

Crystallography

X-ray diffraction investigations were carried out with thesame fragment that was picked from the thin section usedfor the electron-microprobe analysis. The powder X-raydiffraction pattern for uedaite-(Ce) was obtained using aGandolfi camera with a diameter of 114.6 mm and employ-ing Ni-filtered CuKα radiation. The data were recordedon an imaging plate, and processed with a Fuji BAS-2500

Fig. 3. Relationship between Mn and Ca contents in uedaite-(Ce)and allanite-(Ce) from the type locality in Shodoshima Island. Thedata are on the basis of Si = 3 apfu. A: uedaite-(Ce). B: allanite-(Ce)in the rock specimen of type specimen. C: allanite-(Ce) in the otherspecimen from the type locality. The broken line indicates the trendwith a gradient of –1, corresponding the substitution of Mn for Ca.


Table 2. Powder X-ray diffraction data for uedaite-(Ce).

hkl I dmeas. dcalc. hkl I dmeas. dcalc.

001 24 9.23 9.23 401 18 2.18 2.18100 8.10 221 2.15}

26 8.03{ }

19 2.14{

101 7.99 223 2.13101 14 5.09 5.11 023 8 2.10 2.10011 4 4.87 4.87 203 10 2.06 2.06110 15 4.67 4.68 114 1.893}

15 1.890{

200 5 4.04 4.05 224 1.892111 3.82 502 5 1.778 1.782}

6 3.79{

112 3.78 231 6 1.759 1.759

012 7 3.59 3.60 421 1.736}5 1.733

{211 54 3.53 3.53 230 1.730210 9 3.30 3.31 501 4 1.725 1.724201 17 3.24 3.24 206 4 1.697 1.696302 2.93 133 7 1.665 1.667}

100 2.92{

113 2.92 331 6 1.604 1.605020 23 2.87 2.87 406 1.592}

10 1.589{

211 12 2.82 2.82 115 1.589013 2.71 412 9 1.555 1.557120

⎫⎪⎪⎬⎪⎪⎭ 43 2.71

⎧⎪⎪⎪⎨⎪⎪⎪⎩2.71 604 1.467}

7 1.463

{300 2.70 226 1.460

311 39 2.62 2.62 511 5 1.442 1.443202 14 2.55 2.55 040 1.435}

7 1.432{

022 2.44 403 1.434}13 2.42

313 2.42 215 5 1.417 1.416222 13 2.33 2.33 422 6 1.408 1.410114 2.31 624 4 1.305 1.306}

8 2.30{

304 2.30 432 5 1.235 1.236

bio-image analyzer using a computer program written byNakamuta (1999). The powder X-ray diffraction data ofuedaite-(Ce) are given in Table 2. Uedaite-(Ce) is mono-clinic with space group P21/m. The unit-cell parameterswere refined with an internal Si-standard reference mate-rial (NBS #640b) using a computer program by Toraya(1993); a = 8.939(8) Å, b = 5.742(4) Å, c = 10.187(8) Å,β = 115.10(6)◦, V = 473.5(6) Å3, and Z = 2.

The X-ray diffraction intensity data of the single crys-tal selected for structure analysis were collected usinga Rigaku RASA-7R four-circle diffractometer employ-ing graphite-monochromatized MoKα radiation from arotating anode (50 kV, 200 mA). Experimental detailsof the data collection are given in Table 3. Data re-duction to F2

o with Lorentz and polarization correctionsand correction for absorption (φ-scan procedure) werecarried out with a computer program by Dr. KazumasaSugiyama of the University of Tokyo (pers. comm.).The SHELXL-97 software package (Sheldrick, 1997) wasemployed to refine the crystal structure. The scatter-ing factors for the neutral atoms and anomalous dis-persion factors were taken from the International Tablesfor X-ray Crystallography, Volume C (1992). Full-matrixleast-squares refinement was performed by refining the po-sitional parameters, scale factor, and displacement param-eters. The atomic positional parameters of allanite-(Ce)

Table 3. Crystallographic data of uedaite-(Ce) and experimental de-tails.

a (Å) 8.865(3)b (Å) 5.717(3)c (Å) 10.060(3)β (◦) 114.520(17)V (Å3) 463.9(3)Space group P21/mZ 2Formula (Mn0.650Ca0.350)(Ce0.914Fe0.086)(Al0.873Fe0.127)

(Al0.988Fe0.012)(Fe0.875Al0.125)(Si2O7)(SiO4)O(OH)

Dcalc (g/cm3) 4.214μ (cm−1) 8.179Crystal 0.05 × 0.05 × 0.03

dimension (mm)Diffractometer Rigaku AFC-7RRadiation MoKα (graphite-monochromatized)Scan mode, rate 2θ–ω, 2

(◦/ min in ω)2θ range (deg.) 5–70Reflection range 0 � h � 14

−9 � k � 9−16 � l � 14

No. of measured 4305reflections

No. unique 2212reflections

No. of observed 1896reflections

[I > 2σ(I)]Rint 0.0365No. of variable 123

parametersR1 [I > 2σ(I)], 0.0337, 0.0424

R1(all reflections)wR2 0.1081

(all reflections)Weighting 0.1, 0parameters, a, bGoodness of fit 0.858Final Δρmin (e/Å3) –1.80Final Δρmax (e/Å3) 3.45

R1 = Σ ||Fo | − |Fc | | / Σ |Fo |wR2 = {Σ[w(F2

o − F2c )2] / Σ [w(F2

o )2]}0.5w = 1/[σ2(F2

o ) + (aP)2 + bP]P = [2F2

c + F2o ]/3

(Bonazzi & Menchetti, 1995) were used as initial param-eters. The refinement of occupancy parameters for theA and M sites converged to give a structural formulaof: A1(Mn0.650Ca0.350)A2(Ce0.914Fe0.086)M1(Al0.873Fe0.127)M2

(Al0.988Fe0.012)M3(Fe0.875Al0.125)(Si2O7)(SiO4)O(OH). Thefinal positional parameters and anisotropic displacementparameters with equivalent isotropic displacement param-eters are given in Table 4. Selected interatomic distances

Uedaite-(Ce), a new member of the epidote group 265Ta

ble

4.F

inal

atom

icco

ordi

nate

san

ddi

spla

cem

ent

para

met

ers

(Å2).

xy

zU

eqU

11U

22U

33U

23U

13U

12

A1

0.75

371(

11)

0.75

0.14

962(

9)0.

0162

(2)

0.02

56(4

)0.

0095

(3)

0.01

66(4

)0.

00.

0120

(3)

0.0

A2

0.59

398(

3)0.

750.

4296

0(3)

0.01

294(

10)

0.01

143(

13)

0.01

346(

13)

0.01

223(

13)

0.0

0.00

321(

9)0.

0M

10

00

0.01

10(3

)0.

0099

(5)

0.00

71(5

)0.

0147

(6)

0.00

01(4

)0.

0038

(4)

–0.0

006(

3)M

20

00.

50.

0095

(4)

0.00

78(5

)0.

0064

(5)

0.01

33(6

)–0

.000

7(4)

0.00

35(4

)0.

0000

(4)

M3

0.30

676(

8)0.

250.

2106

5(7)

0.01

20(2

)0.

0102

(3)

0.00

96(3

)0.

0130

(3)

0.0

0.00

15(2

)0.

0S

i10.

3406

2(14

)0.

750.

0342

6(13

)0.

0102

(2)

0.00

97(4

)0.

0072

(4)

0.01

21(5

)0.

00.

0028

(4)

0.0

Si2

0.68

819(

14)

0.25

0.27

847(

13)

0.00

99(2

)0.

0095

(4)

0.00

73(4

)0.

0127

(5)

0.0

0.00

43(4

)0.

0S

i30.

1904

2(14

)0.

750.

3238

1(13

)0.

0090

(2)

0.00

85(4

)0.

0077

(4)

0.01

04(5

)0.

00.

0035

(3)

0.0

O1

0.23

24(3

)0.

9902

(4)

0.01

84(3

)0.

0174

(5)

0.01

39(9

)0.

0094

(9)

0.02

72(1

2)–0

.000

8(8)

0.00

69(8

)0.

0026

(7)

O2

0.31

61(3

)0.

9728

(4)

0.36

54(3

)0.

0135

(4)

0.01

34(8

)0.

0100

(8)

0.01

67(9

)–0

.000

5(7)

0.00

57(7

)–0

.002

9(7)

O3

0.79

98(3

)0.

0118

(4)

0.33

14(3

)0.

0164

(4)

0.01

28(8

)0.

0084

(8)

0.02

04(1

1)–0

.000

7(8)

–0.0

007(

8)0.

0016

(7)

O4

0.05

88(4

)0.

250.

1291

(4)

0.01

35(5

)0.

0125

(12)

0.01

12(1

2)0.

0145

(13)

0.0

0.00

35(1

0)0.

0O

50.

0527

(4)

0.75

0.15

18(4

)0.

0151

(6)

0.01

51(1

3)0.

0128

(13)

0.01

56(1

4)0.

00.

0045

(11)

0.0

O6

0.07

51(4

)0.

750.

4176

(4)

0.01

26(5

)0.

0156

(12)

0.00

87(1

1)0.

0188

(14)

0.0

0.01

23(1

1)0.

0O

70.

5102

(4)

0.75

0.17

88(4

)0.

0172

(6)

0.01

62(1

4)0.

0155

(14)

0.01

46(1

4)0.

00.

0010

(11)

0.0

O8

0.54

76(5

)0.

250.

3386

(4)

0.02

34(8

)0.

0151

(14)

0.03

7(2)

0.01

79(1

6)0.

00.

0063

(12)

0.0

O9

0.60

03(5

)0.

250.

0994

(4)

0.02

00(7

)0.

0191

(15)

0.02

60(1

7)0.

0149

(14)

0.0

0.00

69(1

1)0.

0O

100.

0890

(4)

0.25

0.43

00(4

)0.

0122

(5)

0.01

17(1

2)0.

0089

(12)

0.02

00(1

5)0.

00.

0106

(11)

0.0

Refi

ned

occu

panc

y:A

1:0.

650(

19)M

n+

0.35

0Ca;

A2:

0.91

4(6)

Ce+

0.08

6Fe.

M1:

0.87

3(9)

Al+

0.12

7Fe;

M2:

0.98

8(8)

Al+

0.01

2Fe;

M3:

0.87

5(10

)Fe+

0.12

5Al.

Fig. 4. Chondrite-normalized lanthanide distribution pattern ofuedaite-(Ce). The dashed line indicates a fitted line estimated fromthe values of Pr, Nd, Sm and Gd, and shows the trend in the lan-thanide distribution pattern from Pr to the heavier rare earths.

are summarized in Table 5. The highest 7 peaks of residualelectron densities greater than 1.5 e/Å3 were found close tothe A2 and M3 sites with distances less than 0.7 Å. The po-sition of the H atom could not be determined in the presentanalysis. The rather large peaks and holes in residual elec-tron density map may arise from the incomplete absorp-tion correction for diffraction intensity data of the flattenedholotype-specimen, which was cut from the thin section.The bond valences were calculated from the interatomicdistances following the procedure of Brown & Altermatt(1985) using the parameters of Brese & O’Keeffe (1991).The values listed in Table 6 are weighted averages accord-ing to the occupancies in the final refinement (Table 5).

Discussion

Neglect of lanthanides with concentrations below the de-tection limits, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu, re-duce the total number of cations from the ideal value of8 to 7.93 apfu, and lowers the value for the oxygen notbonded to Si from the ideal 1 to 0.85 apfu. Although all ofthe Fe ions were calculated as divalent in Table 1, a partof them may be trivalent Fe3+. The neglect of Fe3+ in thecalculation also lowers the calculated oxygen concentra-tion. The chondrite-normalized lanthanide distribution pat-tern of uedaite-(Ce) is given in Fig. 4. It shows a maximumat Pr decreasing towards heavier rare earth elements. Thetotal amounts of the minor lanthanides, which were not de-termined in the electron microprobe analysis, could be es-timated approximately as 1 wt.% based on the trend shownin the lanthanide distribution pattern.

Manganese is an important constituent of the epidote-group minerals. It occupies the octahedral M1 and M3sites in addition to or alternatively the larger A1 siteas the dominant element in some members, such aspiemontite, manganiandrosite-(La) and khristovite-(Ce)(see Table 7). Manganese is often detected as a minorconstituent replacing Ca in the A1 site and/or Al and Fein the M sites in the other members. Hasegawa (1957)described a Mn-bearing allanite-(Ce) from pegmatite in


Table 5. Interatomic distances (Å).

A1–O3 2.265(3) x2 A2–O7 2.316(4)–O1 2.292(3) x2 –O2 2.456(2) x2–O7 2.297(4) –O10 2.569(3)–O5 2.642(4) –O2 2.606(2) x2–O6 3.002(4) –O3 2.835(3) x2–O9 3.099(4) –O8 2.9774(19) x2–O9 3.115(2) x2 〈A2–O〉10 2.585

〈A1–O〉8 2.519〈A1–O〉10 2.638

M1–O4 1.854(2) x2 M2–O3 1.880(2) x2 M3–O8 1.983(4)–O1 1.991(2) x2 –O10 1.903(2) x2 –O4 2.002(3)–O5 2.000(3) x2 –O6 1.906(2) x2 –O2 2.199(2) x2

〈M1–O〉6 1.948 〈M2–O〉6 1.896 –O1 2.307(3) x2〈M3–O〉6 2.166

Si1–O7 1.600(3) Si2–O8 1.596(4) Si3–O2 1.628(2) x2–O9 1.633(4) –O3 1.637(2) x2 –O5 1.653(4)–O1 1.645(2) x2 –O9 1.639(4) –O6 1.654(3)

〈Si1–O〉4 1.631 〈Si2–O〉4 1.627 〈Si3–O〉4 1.641

Table 6. Bond-valence sums weighted on the occupancies for uedaite-(Ce).

A1 A2 M1 M2 M3 Si1 Si2 Si3 SumO1 0.31x1 0.38x1 0.21x1 0.95x1 1.85

x2 x2 x2 x2

O2 0.41x1 0.28x1 0.99x1 1.96x2 x2 x2

0.28x1

x2

O3 0.34x1 0.15x1 0.50x1 0.97x1 1.96x2 x2 x2 x2

O4 0.56x2 0.47x1 1.59x2 x1

O5 0.12x1 0.37x2 0.92x1 1.78x1 x2 x1

O6 0.05x1 0.46x2 0.92x1 1.89x1 x2 x1

O7 0.31x1 0.60x1 1.07x1 1.98x1 x1 x1

O8 0.10x2 0.49x1 1.08x1 1.77x2 x1 x1

O9 0.04x2 0.98x1 0.96x1 2.05x1 x1 x1

0.03x1

x2

O10 0.30x1 0.47x2 1.24x1 x2

Sum 1.88 2.78 2.62 2.86 1.94 3.95 3.98 3.82

Note: bond-valence parameters are from Brese & O’Keeffe (1991). Contributions of hydrogen atoms are not listed.

Abukuma Massif, Fukushima and Miyagi Prefectures,Japan based on wet chemical analyses. He noticed a trendof negative correlation between Mn and (Ca + Th + Ce +La + Y) in his 8 Mn-bearing allanites from AbukumaMassif, and suggested a substitution of divalent Mn2+

for Ca2+, rather than that of trivalent Mn3+ for Al3+

and Fe3+. Among his samples, one from Ohari, MiyagiPrefecture, Japan gave the following empirical formula(Ca0.45Mn0.51Ce0.93) (Al1.84Fe3+

1.10Fe2+0.12) Si3O11.78 (OH)1.40,

where Mn dominated over Ca. The Mn-analogues ofallanite-(Ce) were described again from the same locality

[(Ca0.46Mn0.69Ce0.94)(Al1.88Fe3+0.28Fe2+

0.96)Si3.05O12(OH)1.48]and from Shiozawa in Abukuma Massif, FukushimaPrefecture, Japan [(Ca0.52Mn0.55Ce0.91) (Al1.82Fe3+

0.26Fe2+0.92)

Si3.06O12 (OH)1.19] (Hasegawa, 1960). No crystallographicdata for the Mn-analogues were given in these descriptions.

Later, Hoshino et al. (2005, 2006) reinvestigated thechemical compositions of allanite-(Ce) in granitic rocksfrom Japan using an electron microprobe analyzer. Theirchemical analyses showed that specimens from Haguri,Shiga Prefecture, Japan are a Mn-analogue of allanite-(Ce),where Mn2+ dominates Ca2+ in the A1 site, e.g.,


Table 7. Comparative data for epidote-group minerals.

a (Å) b (Å) c (Å) β (◦) V (Å3)

Uedaite-(Ce) 8.865(3) 5.717(3) 10.060(3) 114.520(17) 463.9(3)Allanite-(Ce)1 8.894(1) 5.724(1) 10.102(1) 114.87(1) 466.6(1)Manganiandrosite-(La)2 8.896(1) 5.706(1) 10.083(1) 113.88(1) 468.0(1)Manganiandrosite-(Ce)3 8.901(2) 5.738(1) 10.068(2) 113.425(3) 471.81Vanadoandrosite-(Ce)3 8.856(3) 5.729(2) 10.038(4) 113.088(5) 468.5Khristovite-(Ce)4 8.903(6) 5.748(3) 10.107(7) 113.41(5) 477.6(2)Piemontite5 8.857(1) 5.671(1) 10.156(1) 115.29(1) 461.2(1)REE-bearing piemontite6 8.890(2) 5.690(1) 10.135(2) 114.44(2) 466.7(2)Piemontite-(Sr)7 8.849(2) 5.671(2) 10.203(2) 114.63(2) 465.4(2)Dissakisite-(Ce)8 8.905(1) 5.684(1) 10.113(1) 114.62(2) 465.3Dollaseite-(Ce)9 8.934(18) 5.721(7) 10.176(22) 114.31(12) 474.0Clinozoisite10 8.872(1) 5.593(1) 10.144(1) 115.46(1) 454.5(1)Epidote11 8.903(2) 5.649(1) 10.163(1) 115.39(1) 461.8(1)Clinozoisite-(Sr)12 8.882(3) 5.5906(16) 10.210(2) 115.118(18) 459.1(2)Epidote-(Pb)13 8.958(20) 5.665(10) 10.304(20) 114.4(4) 476.2Mukhinite14 8.90 5.61 10.15 115.50 457

A1 A2 M1 M2 M3 Crystal Spacesystem group

Uedaite-(Ce) Mn2+ REE Al Al Fe2+ Monoclinic P21/mAllanite-(Ce)1 Ca REE Al Al Fe2+ Monoclinic P21/mManganiandrosite-(La)2 Mn2+ REE Mn3+ Al Mn2+ Monoclinic P21/mManganiandrosite-(Ce)2 Mn2+ REE Mn3+ Al Mn2+ Monoclinic P21/m

Vanadoandrosite-(Ce)3 Mn2+ REE V3+ Al Mn2+ Monoclinic P21/mKhristovite-(Ce)4 Ca REE Mn3+ Al Mn2+ Monoclinic P21/mPiemontite5 Ca Ca Al Al Mn3+ Monoclinic P21/m

REE-bearing piemontite6 Ca Ca Al Al Mn3+ Monoclinic P21/mPiemontite-(Sr)7 Ca Sr Al Al Mn3+ Monoclinic P21/m

Dissakisite-(Ce)8 Ca REE Al Al Mg Monoclinic P21/mDollaseite-(Ce)9 Ca REE Mg Al Mg Monoclinic P21/mClinozoisite10 Ca Ca Al Al Al Monoclinic P21/m

Epidote11 Ca Ca Al Al Fe3+ Monoclinic P21/mClinozoisite-(Sr)12 Ca Sr Al Al Al Monoclinic P21/mEpidote-(Pb)13 Ca Pb Al Al Fe3+ Monoclinic P21/m

Mukhinite14 Ca Ca Al Al V Monoclinic P21/m

1 SN3 in Bonazzi & Menchetti (1995). 8 Rouse & Peacor (1993).2 AND-517 in Bonazzi et al. (1996). Old name is androsite-(La). 9 Peacor & Dunn (1988).3 Cenki-Tok et al. (2006). 10 CH in Bonazzi & Menchetti (1995).4 Pautov et al. (1993); Sokolova et al. (1991). 11 MBN in Bonazzi & Menchetti (1995).5 BR2P in Bonazzi et al. (1992). 12 Miyajima et al. (2003). Old name is niigataite.6 VA-1a in Bonazzi et al. (1996). 13 Dollase (1971). Old name is hancockite.7 SRPM in Bonazzi et al. (1990). Old name is strontiopiemontite. 14 ICDD #22-1066 (after Shepel & Karpenko, 1969).

(Ca0.321 Mn0.536�0.143) (Y0.098La0.081Ce0.233Pr0.052Nd0.212Sm0.095Gd0.066Dy0.026Th0.038Fe2+

0.046�0.053) (Al0.803Fe3+0.197)

(Al1.000) (Fe2+0.550Fe3+

0.450) (Si2O7) (SiO4)O(OH), where � in-dicates a vacancy, and (Ca0.239Mn0.595�0.166) (Y0.097La0.080 Ce0.235Pr0.053Nd0.215Sm0.095Gd0.070Dy0.026 Th0.032Fe2+

0.085 �0.012) (Al0.793Fe3+0.207)(Al1.000)(Fe2+

0.585Fe3+0.415)

(Si2O7) (SiO4)O(O) (Hoshino et al., 2005). These min-

erals are not metamict in spite of the relatively highcontents of radioactive Th, and produce sharp X-raydiffraction patterns (Hoshino, pers. comm.). These Mn-analogues of allanite with Mn > Ca compositions fromAbukuma and Haguri can also be considered as uedaite-(Ce). Consequently, uedaite-(Ce) is not a rare mineral ingranites of Japanese Islands.


The crystal structure of uedaite-(Ce) is isostructuralwith allanite-(Ce) (Ueda, 1955; Bonazzi & Menchetti,1995; Hoshino et al., 2005). The crystal structure ofuedaite-(Ce) consists of two types of chains of edge-sharing MO6 octahedra. The diortho (Si2O7) groupsand isolated SiO4 tetrahedra cross-link the chains toform a three-dimensional framework having large voidsfor the A site cations, such as Mn, Ca and REE. Therefinement of occupancy parameters for the A and Msites showed the dominance of Mn at the A1 site andselective occupation of Al in the M1 site as the structuralformula; A1 (Mn0.650Ca0.350)A2 (Ce0.914Fe0.086)M1 (Al0.873Fe0.127)M2 (Al0.988Fe0.012)M3 (Fe0.875Al0.125) (Si2O7) (SiO4)O(OH).

Application of the structural formula onto the em-pirical chemical formula leads the crystal chemistry ofuedaite-(Ce): (Mn0.51Ca0.26Fe0.23)(Ce0.39Nd0.23La0.11Pr0.07Sm0.05Y0.04Gd0.02Th0.01) (Al0.85Fe0.15)(Al0.96Fe0.04)(Al0.08Fe0.92Mg0.01)(Si2O7) (SiO4)O0.85(OH).

Bonazzi et al. (1996) reported that the high contentof Mn2+ in the A1 site of manganiandrosite-(La) modi-fies the arrangement of the coordinating O atoms. Theynoticed the shift of the seventh neighbor (O6) awayfrom the A1 site. This rearrangement was quantified bythe size of the gap between the seventh and the sixthdistance (A1–O5 and A1–O6). The gap increases from0.316 Å in piemontite (Dollase, 1969) to 0.490 and0.517 Å in manganiandrosite-(La) (Bonazzi et al., 1996)and vanadoandrosite-(Ce) (Cenki-Tok et al., 2006), respec-tively. The gap in uedaite-(Ce), 0.360 Å (present study)is greater than that of allanite-(Ce), 0.275 Å (Bonazzi &Menchetti, 1995). The mean [6]〈A1-O〉 distance in uedaite-(Ce), 2.342 Å (present study), is lower than that of allanite-(Ce), 2.398 Å (Bonazzi & Menchetti, 1995). This rela-tionship between uedaite-(Ce) and allanite-(Ce) is similarto that between manganiandrosite-(La) and piemontite re-ported by Bonazzi et al. (1996).

Kartashov et al. (2002) reported that the coordination ofthe A1 site in ferriallanite-(Ce) is 6 + 1 + 3, according totheir charge distribution calculation. In the crystal structureof uedaite-(Ce), the interatomic distances from the centralA1 cation to the seventh, eighth and ninth neighbor oxy-gen atoms are comparable (3.099(4) and 2 × 3.115(2) Å,see Table 5). The empirical formula with 3.02 apfu for Sisuggests no significant vacancy at the A sites in uedaite-(Ce). The bond-valence calculation for uedaite-(Ce) with-out bonds to the three O9 atoms resulted in a low valueof the bond-valence sum for A1, 1.78 valence units (v.u.)(Table 6). The low bond-valence sum slightly improved byadding the three O9 atoms to the coordination of A1 yield-ing, 1.88 v.u., which is closer to the ideal 2 v.u.

The low value of the bond-valence sum for O10, 1.24v.u., is related to the OH nature of O10, as found in mostmembers of the epidote-group minerals. The O4 atom withlow 1.59 v.u. acts as acceptor of the hydrogen bond fromthe O10. Hoshino et al. (2005) interpreted the undersatura-tions of bond-valence sums for O2 and O8 in allanite-(Ce)(1.81 and 1.75 v.u., respectively) as the effect of vacan-cies at the A2 site. In the crystal structure of uedaite-(Ce),

a slight undersaturation is apparently indicated for the O8site (1.77 v.u.), but not for the O2 site (1.96 v.u.).

Uedaite-(Ce) is a member of the allanite subgroup ofthe epidote group. Criteria for the allanite subgroup are[M3++ M4+]A2 > 0.50, and [M2+]M3 > 0.50 (Armbrusteret al., 2006). Uedaite-(Ce) is the Mn2+-dominant analogueof allanite-(Ce), with substitution of Mn for Ca in the A1position, but Mn does not substitute for Al or Fe in the Mpositions. Uedaite-(Ce) cannot be a member of the REE-bearing dollaseite subgroup because of the absence of flu-orine, so that the amount of Fe is not sufficient to take partas Fe2+ in two heterovalent substitutions (see also Table 7).

According to the recently approved nomenclature schemefor epidote-group minerals (Armbruster et al., 2006), mem-bers of the allanite subgroup have no prefix added to theroot name if the M1 position is occupied by aluminum, anda new root name is necessary if the A1 position is occupiedby another element than Ca (see Table 3 of the epidote re-port; Armbruster et al., 2006). The new root name is forthe late Prof. Tateo Ueda (1912–2000), who was the first tosolve the crystal structure of allanite (Ueda, 1955). The suf-fix indicating the predominant REE, Ce, is given accordingto the Levinson modifier.

Acknowledgements: We thank Prof. Thomas Armbruster,Prof. Uwe Kolitsch and Dr. Christian Chopin for their help-ful and accurate reviews.

References

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Received 4 July 2007Modified version received 5 November 2007Accepted 23 November 2007

uedaite-(ce), a new member of the epidote group with mn at the a site, from shodoshima, kagawa...

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