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Ca-Mg-Fe-rich rhodonite from the Morro da Mina mine, Conselheiro Lafaiete, Minas Gerais, Brazil.

Large and superb crystals of translucent to gemmy, brilliant red rhodonite found in a manganese mine near Conselheiro Lafaiete, Brazil have been reaching the mineral market in recent years. The crystals have been analyzed and proved to be significantly enriched in calcium, magnesium and iron.

INTRODUCTION

The city of Conselheiro Lafaiete (20[degrees]40'S, 43[degrees]8'W) is located about 100 km south of Belo Horizonte in the interior of Minas Gerais, Brazil. It lies in the southern section of the Quadrilatero Ferrifero ("Iron Quadrangle"), a 7000 [km.sup.2] section of the Sao Francisco craton, characterized by Archean gneisses, Neoarchean greenstones and Paleoproterozoic sediments. The area around Conselheiro Lafaiete is part of the highly folded Barbacena Greenstone Belt, which has been intruded by a series of granodiorites and aplitic to pegmatitic dikes (Pires, 1977), and is host to a number of significant manganese deposits (Derby, 1901; Pires, 1977, 1983; Pires and Cabral, 2001).

The major mine in the district is the Morro da Mina open pit (opened in 1894), which produced some 12 million tons of oxide and silicate ore between 1902 and 1995 and is currently operated by Companhia Vale do Rio Doce. The deposit is characterized by rocks known as gondites, composed of quartz and spessartine, and queluzites, which are rich in spessartine, rhodonite, and rhodochro-site. Dominant primary manganese minerals include spessartine, tephroite, rhodonite, pyroxmangite, neotocite, bementite, Mn-rich cummingtonite, rhodochrosite and Mn-rich apatite (Pires, 1977, 1983).

[FIGURE 1 OMITTED]

Of particular interest to this study is a hydrothermally derived assemblage composed of spessartine, rhodonite and asbestiform Mn-rich cummingtonite (Pires, 1977). Recently, a considerable quantity of deep pink, gem-quality material supposed to be rhodonite from the Morro da Mina mine has appeared on the specimen market. The rhodonite is invested with varying amounts of cummingtonite needles, but some of the rhodonite is free of such inclusions.

Thomas Moore (in preparation), in his compendious Mineral Discoveries 1960-2010, writes of the occurrence as follows:
  Rhodonite crystals "of gem quality" from Conselheiro Lafaiete, Minas
  Gerais have been reported as early as 1971. In the second half of the
  1990's, a few specimens of rhodonite emerged from the Mn-rich,
  spessartine/amphibole/rhodonite/pyroxmangite skarn at Conselheiro
  Lafaiete; they are miniature-size, medium pink to pink-red aggregates
  of parallel, tightly intergrown, bladed crystals (reported in "What's
  new in minerals" in 1995 and 1999). Beginning around 2005, further
  work was done at the mine with a view to extracting rhodonite
  specimens from the Mn-rich skarn deposit, and at the 2006 Tucson Show
  a few fine rhodonite specimens were offered by an American dealer.
  They are thumbnails and miniatures, and two extraordinary specimens;
  one is a 5.2-cm cluster of gemmy, deep pink rhodonite crystals with a
  single, sharp individual measuring 2 X 3 cm; the other is a parallel
  group of two well-terminated crystals measuring 6 cm. These specimens
  are laboriously prepared by removing the hard mixture of amphibole,
  spessartine, and massive rhodonite/pyroxmangite from around the
  calcite-filled vugs which harbor the rhodonite crystals.


Both of the major specimens mentioned by Moore are pictured here.

Because of a question surrounding the true identity of the rhodonite specimens (Luiz Menezes, personal communication), we have investigated the material using a combination of electron micro-probe, X-ray powder diffraction and single-crystal X-ray techniques. The study, results of which are reported below, has shown that the material in question is indeed a Ca-Mg-Fe-rich rhodonite.

EXPERIMENTAL

Crystals of rhodonite from the Morro da Mina mine were supplied by Luiz Menezes. A crystal fragment free of cummingtonite inclusions was embedded in epoxy resin, polished and carbon-coated. No zoning of the rhodonite was evident in BSE (back-scattered electron) images, but a single small inclusion some 30 [micro]m across was noted. Five spot analyses of rhodonite and four of the inclusion were carried out using a Jeol 8600 electron microprobe (WDS mode, 30 kV, 20 nA, 3 [micro]m beam diameter). Analytical data are given in Table 1. The empirical formula ofg the rhodonite based on 5 (Si,Al)[O.sub.4] groups is:

([Mn.sub.3.76][Ca.sub.0.50][Mg.sub.0.34][Fe.sub.0.33])[.sub.[SIGMA]4.93]([Si.sub.4.97][Al.0.03])[O.sub.15],

and the simplified formula normalized for an [M.sup.2+] cation total of 5 pfu is:

([Mn.sub.3.81][Ca.sub.0.51][Mg.sub.0.35][Fe.sub.0.33])[Si.sub.5][O.sub.15].

The small inclusion has an empirical formula of:

([Mn.sub.3.69][Ca.sub.0.51][Fe.sub.0.33][Mg.sub.0.32])[.sub.[SIGMA][zeta]4.85]([Si.4.97][Al.sub.0.03])[O.sub.15],

with the cation deficiency presumably accounted for by appropriate protonation of some of the silicate oxygen atoms. This phase was not studied further.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Powder X-ray diffraction data (Table 2) were recorded using a Philips PW1925-20 powder diffractometer (Cu K[alpha] radiation, [lambda] = 1.5406 [Angstrom], with pure Si as internal standard). For the single-crystal structure analysis, a cleavage fragment 0.45 X 0.45 X 0.30 mm in size was mounted on a Bruker SMART CCD diffractometer. A careful inspection of the reflection record showed that only one phase is present, i.e., the crystal used is free of inclusions. Unit cell dimensions were determined by least-squares refinement of the complete data set and are listed in Table 3 together with associated crystal data. All data were collected at 273(2) K using graphite-monochromatized Mo K[alpha] radiation, corrected for Lorentz and polarization effects, and an absorption correction using SADABS was applied (Sheldrick, 1996). The structure was completely determined by direct methods using SHELXS (Sheldrick, 1997a) and refined on [F.sup.2] by full-matrix least-squares methods using SHELXL97 (Sheldrick, 1997b). All atoms were found to be in positions similar to the analogous atoms in the magnesian rhodonite reported by Peacor et al. (1978), and an initial isotropic refinement assuming all five metal sites were fully occupied by Mn gave R1 = 0.051 with no unusual thermal parameters. Allowing the five metal site occupancies to also vary at this stage reduced R1 to 0.037 and gave a good indication of the electron density present at each of the five metal sites. This was then used in conjunction with the electron microprobe analyses to deduce the probable distribution of Mn, Mg, Ca and Fe in each of the sites, noting also the preference of the various different metal ions present to occupy these five non-equivalent metal sites (as discussed below) and the need to achieve acceptable thermal parameters for each site. A final anisotropic refinement of this distributed metal ion model resulted in most acceptable and nearly uniform [U.sub.eq] values for each of the five metal sites and an R1 of 0.0242 and wR2 of 0.0646. The weighting scheme used was w = 1/([[sigma].sup.2][F.sub.o.sup.2] + 0.0364[P.sup.2] + 0.600P), where P = ([F.sub.o.sup.2] + 2[F.sub.c.sup.2])/3, as defined by SHELXL97 (Sheldrick 1997b). Crystal data and refinement details are given in Table 3. Final atomic parameters are listed in Table 4, anisotropic displacement parameters in Table 5, and selected bond lengths in Table 6.

RESULTS AND DISCUSSION

Analyses of rhodonite from the Morro da Mina mine (Table 1) are entirely consistent with the formulation of the mineral, with enrichment of Ca, Mg and Fe. Powder X-ray diffraction data listed in Table 2 are compared with those for an Mg-rich rhodonite from the Balmat mine No. 4, New York, USA, which has the composition ([Mn.sub.3.73][Mg.sub.0.73][Ca.sub.0.51][Fe.sub.0.03])[Si.sub.5][O.sub.15] (Peacor et al., 1978; JCPD File 83-2212). Powder X-ray data for rhodonite are quite sensitive to small variations in unit cell constants (Viswanathan and Harneit, 1986; Pinckney and Burnham, 1988), but those for the two cases above are very similar, due to the analogous Ca and Mg+Fe contents.

A number of studies have been directed towards understanding the distribution of cations among the five non-equivalent sites in rhodonite (Peacor and Niizeki, 1963; Dickson, 1975; Marshall and Runciman, 1975; Ohashi and Finger, 1975a,b; Peacor et al., 1978; Nelson and Griffen 2005). It is clear that Ca substitutes in the M5 site, which is 7-coordinated and distorted. Fe distribution has been studied using Mossbauer spectroscopy (Dickson, 1975) and Fe(II) has been found to be present in all five sites, but not equally. Although Dickson (1975) was somewhat equivocal about the site preferences for Fe, it is evident that site occupancies for M1, M2 and M3 sites are approximately equal and M4 is slightly preferred; the M5 site is least preferred. Based on fitted intensities in the Mossbauer spectra at 77 K of a number of samples with varying Fe contents, the relative site occupancies for Fe in sites M1 to M5 are 0.67:0.67:0.67:1:0.24, respectively. We have distributed Fe in the present structure using the same regime, but note that with Mn dominant in sites M1 to M4 and almost equal to Ca in M5, the one-electron difference between Mn and Fe will have negligible bearing on the temperature factors, whatever the relative Fe:Mn distribution. Mg has been distributed over the five sites in the following way. For sites M1 to M3, sof values were assigned to give comparable U(eq) values, and for M4 and M5 to account for the remainder in such a way as to mimic slightly higher relative U(eq) values in line with the structure determination of Peacor et al. (1978). We cannot be absolutely certain of the sof values for Fe and Mg, but the structure refined sensibly and no anomalous patterns emerged in the anisotropic thermal parameters or the final difference map as a result of the adopted procedure.

There is no discrepancy in the structure as compared with others that have been reported for rhodonite (Peacor and Niizeki, 1963; Ohashi and Finger, 1975a,b; Peacor et al., 1978; Pertlik and Zahiri, 1999; Nelson and Griffen 2005). In the present structure, and in line with the above reports, the Ml, M2 and M3 sites are all quasi-octahedral, with the M4 site being somewhat more distorted to give a [5+1] coordination sphere (Table 6). The M5 site, which accommodates the larger [Ca.sup.2+] ion, is 7-coordinated, with the usual [4+3] distribution of M-O bonds. Table 6 also indicates that the usual geometry of the silicate chain is present as evidenced by the Si-O bond lengths. For further structural details, the supplementary material should be consulted.

SUPPLEMENTARY MATERIAL

Full lists of crystallographic data excluding structure factor tables have been deposited with the Inorganic Crystal Structure Database (ICSD), Fachinformationszentrum, Karlsruhe, Germany; CRYSDATA@FIZ-Karlsruhe.DE. Any request to the ICSD for this material should quote the full literature citation and the CSD number 418082. Lists of observed and calculated structure factors are available from the authors upon request.

REFERENCES

DERBY, O. A. (1901) On the manganese ore deposits of the Queluz (Lafayette) District, Minas Geraes, Brazil. American Journal of Science, 4th Series, 12, 18-32.

DICKSON, B. L. (1975) The iron distribution in rhodonite. American Mineralogist, 60, 98-104.

MARSHALL, M., and RUNCIMAN, W. A. (1975) The absorption spectrum of rhodonite. American Mineralogist, 60, 88-97.

MOORE, T. P. (in preparation) Mineral Discoveries 1960-2010. To be published by the Mineralogical Record, Tucson.

NELSON, W. R., and GRIFFEN, D. T. (2005) Crystal chemistry of Zn-rich rhodonite ("fowlerite"). American Mineralogist, 90, 969-983.

OHASHI, Y., and FINGER, L. W. (1975a) Pyroxenoids: a variation in chemistry of natural rhodonites and pyroxmangites. Carnegie Institution of Washington, Year Book, 74, 561-564.

OHASHI, Y., and FINGER, L. W. (1975b) Pyroxenoids: a comparison of refined structures of rhodonite and pyroxmangite. Carnegie Institution of Washington, Year Book, 74, 564-569.

PEACOR, D. R., and NIIZEKI, N. (1963) The redetermination and refinement of the crystal structure of rhodonite, (Mn,Ca)Si[O.sub.3]. Zeitschrift fur Kristallographie, 119, 98-116.

PEACOR, D. R., ESSENE, E. J., BROWN, P. E., and WINTER, G. A. (1978) The crystal chemistry and petrogenesis of a magnesian rhodonite. American Mineralogist, 63, 1137-1142.

PERTLIK, F., and ZAHIRI, R. (1999) Rhodonite with a low calcium content: crystal structure determination and crystal chemical calculations. Monatshefte fur Chemie, 130, 257-265.

PINCKNEY, L. R., and BURNHAM, C. W. (1988) Effects of compositional variation on the crystal structures of pyroxmangite and rhodonite. American Mineralogist, 73, 798-808.

PIRES, F. R. M. (1977) Geologia do Distrito Manganesifero de Conselheiro Lafaiete, Minas Gerais. MSc Thesis, Universidade Federal do Rio de Janeiro.

PIRES, F. R. M. (1983) Manganese mineral parageneses in the Lafaiete District, Minas Gerais, Brazil. Anais da Academia Brasileira de Ciencias, 55, 272-285.

PIRES, F. R. M., and CABRAL, A. R. (2001). Estudos de Orville Derby sobre os depositos manganesfferos do Brasil--edicao comemorativa dos 150 anos de nascimento do cientista. Revista Escola de Minas, 54, 205-209.

SHELDRICK, G. M. (1996) SADABS. Empirical Absorption Correction Program for Area Detector Data. University of Gottingen, Gottingen, Germany.

SHELDRICK, G. M. (1997a) SHELXS97, A Program for the Solution of Crystal Structures. University of Gottingen, Gottingen, Germany.

SHELDRICK, G. M. (1997b) SHELXL97, A Program for the Refinement of Crystal Structures. University of Gottingen, Gottingen, Germany.

VISWANATHAN, K., and HARNEIT, O. (1986) Lattice expansion and ionic substitution in common pyroxenoids. Contributions to Mineralogy and Petrology, 94, 238-244.

Peter Leverett*, Peter A. Williams

School of Natural Sciences

University of Western Sydney

Locked Bag 1797

Penrith South DC NSW 1797, Australia

and

David E. Hibbs

School of Pharmacy

University of Sydney

NSW 2006, Australia

*e-mail: p.leverett@uws.edu.au
Table 1. Analytical data (wt%) for rhodonite and pyroxenoid inclusion.

Rhodonite            1      2      3       4       5      av.

MgO                   2.06   1.97    2.58    2.03   1.99   2.13
[Al.sub.2][O.sub.3]   0.45   0.59    0.47    0.46   0.49   0.49
Si[O.sub.2]          46.94  46.45   46.77   47.01  47.01  46.84
CaO                   4.45   4.32    4.37    4.33   4.52   4.40
MnO                  41.86  40.84   42.55   42.73  41.41  41.88
FeO                   3.87   3.66    3.78    3.84   3.72   3.77
Total                99.63  97.83  100.52  100.40  99.14  99.50

Inclusion            1      2      3      4      av.

MgO                   2.08   1.99   1.97   1.97   2.00
[Al.sub.2][O.sub.3]   0.46   0.58   0.47   0.39   0.48
Si[O.sub.2]          46.71  47.07  47.45  47.15  47.10
CaO                   4.43   4.36   4.60   4.56   4.49
MnO                  41.00  41.80  41.33  41.20  41.33
FeO                   3.78   3.85   3.78   3.60   3.75
Total                98.46  99.65  99.60  98.87  99.15

Table 2. Powder X-ray diffraction data for rhodonite.

Morro da Mina (a)                    Balmat mine No. 4 (b)
[d.sub.obs]/[Angstrom]  [I.sub.rel]  [d.sub.obs]/[Angstrom]  [I.sub.rel]

7.146                    44          7.1                      50
6.733                    24          6.67                     15
4.783                    34          4.76                     50
4.126                     9          4.12                      8
3.817                    16          3.81                     15
3.562                    61          3.55                     85
3.406                    13          3.40                     11
3.336                    32
3.255                    15          3.25                     12
3.138                    58          3.13                     76
3.091                    89          3.08                    100
2.970                   100          2.969                   100
2.927                    50          2.925                    63
2.805                    16          2.809                    10
2.783                    22          2.781                    26
2.759                    26          2.748                    46
2.651                    16          2.648                    18
2.597                    39          2.593                    34
2.540                    11          2.535                     7
2.513                    55          2.505                    65
2.452                    10
2.430                     9          2.427                    10
2.398                     8          2.382                     8
2.372                    17          2.369                    16
2.316                     9          2.312                     4
                                     2.259                     3
2.223                    68          2.220                    24
                                     2.208                     8
2.178                    51          2.178                    53
2.159                    10          2.152                     6
2.114                    15          2.113                    11
2.089                    13          2.084                     7
2.066                    10          2.061                     8
2.046                     6
1.980                    10
1.950                     6          1.949                     4
1.894                    17          1.892                    11
1.864                    20          1.860                    13
                                     1.831                     7
plus 27 lines to 1.277

(a) This work; ([Mn.sub.3.81][Ca.sub.0.51][Mg.sub.0.35][Fe.sub.033])
[Si.sub.5][O.sub.15],
(b) Peacor et al., 1978; ([Mn.sub.3.73][Mg.sub.0.73][Ca.sub.0.51]
[Fe.sub.0.03])[Si.sub.5][O.sub.15].

Table 3. Crystal data and structure refinement details for rhodonite.

Empirical formula             ([Mn.sub.3.81][Ca.sub.0.51][Fe.sub.0.33]
                                [Mg.sub.0.35])[Si.sub.5][O.sub.15]
Formula weight                637.15
Temperature                   273(2) K
Wavelength                    0.71073 [Angstrom]
Crystal system                Triclinic
Space group                   P [bar.1]
Unit cell dimensions          a = 6.6818(13) [Angstrom] [alpha] =
                                105.49(3)[degrees]
                              b = 7.6330(15) [Angstrom] [beta] =
                                92.49(3)[degrees]
                              c = 11.795(2) [Angstrom] [gamma] =
                                94.01(3)[degrees]
Volume                        577.1(2) [[Angstrom].sup.3]
Z                             2
Density (calculated)          3.667 Mg [m.sup.-3]
Absorption coefficient        5.341 [mm.sup.-1]
F(000)                        616
Crystal size                  0.45 X 0.45 X 0.45 mm
[theta] range for data        1.80 to 28.62[degrees]
  collection
Index ranges                  -9 [less than or equal to]
                              h [less than or equal to] 8,
                              -9 [less than or equal to]
                              k [less than or equal to] 9,
                              -15 [less than or equal to]
                              1 [less than or equal to] 15
Reflections collected         5685
Independent reflections       2675 [R(int) = 0.0184]
Completeness to [theta] =     90.7%
  28.62[degrees]
Refinement method             Full-matrix least-squares on [F.sup.2]
Data/restraints/parameters    2675/0/227
Goodness-of-fit on [F.sup.2]  1.004
Final R indices               R1 = 0.0242, wR2 = 0.0623
  [I>2[sigma](I)]
R indices (all data)          R1 = 0.0286, wR2 = 0.0646
Extinction coefficient        0.0040(5)
Largest diff. peak and hole   0.491 and -0.533 e [[Angstrom].sup.-3]

Table 4. Atomic coordinates (X [10.sup.4]), site occupancy factors (sof)
and equivalent isotropic displacement parameters ([[Angstrom].sup.2] x
[10.sup.3] for rhodonite, U(eq) is defined as one third of the trace of
the orthogonalized [U.sub.ij] tensor. All silicon and oxygen atom sites
are fully occupied.

       x/a       y/b       z/c       sof   U(eq)

Mn(1)   1260(1)   3164(1)   4448(1)  0.88   6(1)
Mg(1)   1260(1)   3164(1)   4448(1)  0.05   6(1)
Fe(1)   1260(1)   3164(1)   4448(1)  0.07   6(1)
Mn(2)   -302(1)   8822(1)   8521(1)  0.89   6(1)
Mg(2)   -302(1)   8822(1)   8521(1)  0.04   6(1)
Fe(2)   -302(1)   8822(1)   8521(1)  0.07   6(1)
Mn(3)   1877(1)   5101(1)   7300(1)  0.87   6(1)
Mg(3)   1877(1)   5101(1)   7300(1)  0.06   6(1)
Fe(3)   1877(1)   5101(1)   7300(1)  0.07   6(1)
Mn(4)   2046(1)   7011(1)  10246(1)  0.75   7(1)
Mg(4)   2046(1)   7011(1)  10246(1)  0.15   7(1)
Fe(4)   2046(1)   7011(1)  10246(1)  0.10   7(1)
Mn(5)   3549(1)   -437(1)   3015(1)  0.42  10(1)
Ca(5)   3549(1)   -437(1)   3015(1)  0.51  10(1)
Fe(5)   3549(1)   -437(1)   3015(1)  0.02  10(1)
Mg(5)   3549(1)   -437(1)   3015(1)  0.05  10(1)
Si(1)   2938(1)   5420(1)   2626(1)         7(1)
Si(2)   3628(1)   7355(1)   5307(1)         6(1)
Si(3)   1537(1)    763(1)   6542(1)         6(1)
Si(4)   5038(1)   7814(1)   8751(1)         6(1)
Si(5)   2463(1)  12561(1)   9110(1)         7(1)
O(1)    1099(3)   2514(2)   6113(2)         8(1)
0(2)    1933(3)   5999(2)   5641(2)         9(1)
0(3)     396(3)    440(2)   3210(2)         8(1)
0(4)    1063(3)   4006(2)   2690(2)         8(1)
0(5)     577(3)  11579(2)   9603(2)         8(1)
0(6)    5161(3)   5794(2)   7797(2)         8(1)
0(7)    1926(3)   4525(2)   9025(2)         9(1)
0(8)    3767(3)   6832(2)   3885(2)        10(1)
0(9)   -3388(3)   9348(2)   8543(2)         8(1)
0(10)   4183(3)   2440(3)   4074(2)        15(1)
O(11)   2998(3)   1396(2)   7778(2)         9(1)
0(12)   5521(3)   7437(2)  10047(2)         8(1)
0(13)   2657(3)   8007(2)   8688(2)         8(1)
0(14)   2551(3)   6805(3)  11862(2)        12(1)
0(15)   2940(3)   9467(2)   5621(2)        12(1)

Table 5. Anisotropic displacement parameters ([[Angstrom].sup.2] X
[10.sup.3]) for rhodonite. The anisotropic displacement factor exponent
takes the form -2[[pi].sup.2][[h.sup.2][a.sup.*2][U.sub.11] + ... +
2hka*b*[U.sub.12]].

       [U.sub.11]  [U.sub.22]  [U.sub.33]

M(1)    6(1)        7(1)        6(1)
M(2)    5(1)        7(1)        6(1)
M(3)    5(1)        6(1)        6(1)
M(4)    8(1)        9(1)        5(1)
M(5)    9(1)        6(1)       15(1)
Si(1)   6(1)        8(1)        6(1)
Si(2)   6(1)        9(1)        5(1)
Si(3)   6(1)        6(1)        6(1)
Si(4)   5(1)        8(1)        6(1)
Si(5)   6(1)        8(1)        6(1)
O(1)    9(1)        8(1)        8(1)
O(2)    9(1)        9(1)        8(1)
O(3)    7(1)        9(1)        8(1)
O(4)    5(1)        9(1)        9(1)
O(5)    7(1)        9(1)        8(1)
O(6)    7(1)        9(1)        7(1)
O(7)   10(1)        9(1)        9(1)
O(8)   11(1)       10(1)        7(1)
O(9)    8(1)        9(1)        8(1)
O(10)   9(1)       27(1)       12(1)
O(11)   7(1)       10(1)        7(1)
O(12)   7(1)       10(1)        7(1)
O(13)   6(1)        8(1)       10(1)
O(14)  11(1)       15(1)       11(1)
O(15)  14(1)        6(1)       16(1)

       [U.sub.23]  [U.sub.13]  [U.sub.12]

M(1)    1(1)        0(1)        0(1)
M(2)    1(1)        0(1)        1(1)
M(3)    1(1)       -1(1)        1(1)
M(4)    2(1)        1(1)        4(1)
M(5)   -1(1)        4(1)       -1(1)
Si(1)   2(1)        1(1)        1(1)
Si(2)   2(1)        0(1)        0(1)
Si(3)   1(1)        0(1)        0(1)
Si(4)   1(1)        0(1)        1(1)
Si(5)   2(1)        0(1)        0(1)
O(1)    3(1)        0(1)        1(1)
O(2)    3(1)        1(1)        0(1)
O(3)    2(1)        0(1)       -1(1)
O(4)    2(1)        1(1)        1(1)
O(5)    3(1)        1(1)        1(1)
O(6)    0(1)        2(1)        0(1)
O(7)    4(1)       -1(1)        1(1)
O(8)    0(1)        1(1)       -2(1)
O(9)    3(1)        1(1)        0(1)
O(10)  10(1)       -1(1)        1(1)
O(11)   1(1)       -1(1)        0(1)
O(12)   3(1)       -1(1)        0(1)
O(13)   3(1)        1(1)        1(1)
O(14)   6(1)       -1(1)        2(1)
O(15)   1(1)        8(1)        1(1)

Table 6. Selected bond lengths [[Angstrom]] for rhodonite.

M(1)-O(10)     2.100(2)  M(2)-O(13)      2.130(2)
M(1)-O(1)      2.155(2)  M(2)-O(5)       2.175(2)
M(1)-O(3)      2.220(2)  M(2)-O(4)#1     2.257(2)
M(1)-O(2)      2.246(2)  M(2)-O(3)#1     2.258(2)
M(1)-O(2)#1    2.276(2)  M(2)-O(5)#2     2.327(2)
M(1)-O(4)      2.330(2)  Mn(2)-O(9)      2.128(2)
M(3)-O(1)      2.109(2)  M(4)-O(14)      1.971(2)
M(3)-O(4)#1    2.123(2)  M(4)-O(7)       2.046(2)
M(3)-O(7)      2.193(2)  M(4)-O(5)#2     2.110(2)
M(3)-O(6)      2.236(2)  M(4)-O(13)      2.211(2)
M(3)-O(2)      2.241(2)  M(4)-O(12)      2.352(2)
M(3)-O(13)     2.386(2)  M(4)-O(9)#2     2.827(2)
M(5)-O(9)#1    2.211(2)
M(5)-O(14)#3   2.219(2)
M(5)-O(10)     2.218(2)
M(5)-O(3)      2.258(2)  Si(1)-O(14)#7   1.589(2)
M(5)-O(8)#4    2.568(2)  Si(1)-O(4)      1.614(2)
M(5)-O(11)#5   2.606(2)  Si(1)-O(8)      1.632(2)
M(5)-O(15)#6   2.727(2)  Si(1)-O(6)#6    1.641(2)
Si(2)-O(10)#5  1.585(2)  Si(3)-O(1)      1.591(2)
Si(2)-O(2)     1.613(2)  Si(3)-O(3)#9    1.614(2)
Si(2)-O(8)     1.626(2)  Si(3)-O(15)#4   1.638(2)
Si(2)-O(15)    1.657(2)  Si(3)-O-(11)    1.657(2)
Si(4)-O(9)#10  1.594(2)  Si(5)-O(7)#8    1.594(2)
Si(4)-O(13)    1.609(2)  Si(5)-O(5)      1.628(2)
Si(4)-O(12)    1.652(2)  Si(5)-O(12)#11  1.639(2)
Si(4)-O(6)     1.657(2)  Si(5)-O(11)#8   1.654(2)

Symmetry transformations used to generate equivalent atoms are #1: -x,
-y+1,-z+1; #2: -x,-y+2,-z+2; #3: x,y-1,z-1; #4: x,y-1,z; #5: -x+1,-y,
-z+1; #6: -x+1,-y+1,-z+1, #7: x,y,z-1; #8: x,y+1,z; #9: -x,-y,-z+1 #10:
x+1,y,z; #11: -x+1,-y+2,-z+2; #12: x-1,y,z.
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Author:Leverett, Peter; Williams, Peter A.; Hibbs, David E.
Publication:The Mineralogical Record
Article Type:Report
Geographic Code:3BRAZ
Date:Mar 1, 2008
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