Zeitschrift

fUr Kristallographie

197, 97 -1 06 (1991)(0 by R. Olden bourg Verlag, Miinchen 1991 - 0044-2968/91 $ 3.00+0.00

Gravegliaite,

MnS03. 3 H20, a new mineralfrom Val Graveglia (Northern Apennines, Italy)
R. Basso, G. Lucchetti
Dipartimento di Scienze delia Terra dell'Universita,
Corso Europa, 26, 1-16132 Genova, Italy

and A. Palenzona
Istituto di Chimica Fisica dell'Universita,
Received: November

Corso Europa, 26, 1-16132 Genova,

Italy

12. 1990

Gravegliaite f New mineralf Sulfite f Powder pattern f Structure refinement
Abstract. A crystallographic and crystal chemical study has been performed
on a new mineral, an orthorhombic MnS03 . 3 H20 occurring in manganese ores at the Gambatesa Mine (Val Graveglia, Italy), associated withtephroite, bementite, braunite, hausmannite and hematite. Gravegliaite,
appearing mainly as few radial aggregates of prismatic crystals, elongatedparallel to [010] and up to 0.5 mm long, crystallizes in Pllma space groupwith a = 9.763(1) A, b = 5.635(1) A and c = 9.558(1) A. It is colourless,transparent, optically biaxial and nonpleochroic with Ila = 1.590, IIp =1.596, Ily = 1.636 and 2 Vy = 41" (Z=h). The strongest lines in the powder
pattern are (d A) 6.83, 4.33 and 3.43. Microprobe analyses reveal a goodcompositional homogeneity and a quasi-ideal chemical composition. The
crystal structure refinement confirms this mineral to be the natural analogueof synthetic MnS03 . 3 H20 described by previous authors. The attempt
to localize hydrogen atoms and to assign hydrogen bonds is discussed, sincehydrogen bonds seem to play the major role in assuring cohesion to thestructure.

Introduction
The mineralizations occurring in the manganesiferous layers of the radiolarian cherts in the ophiolitic sequences from the Eastern Liguria (Italy)
are well known for the abundance of mineral species which originatedduring various crystallization phases (Cortesogno, Lucchetti, Penco, 1979;

98

R. Basso, G. Lucchetti and A. Palenzona

Lucchetti, Cortesogno and Palenzona, 1988). During recent research a
significant number of rare minerals were identified, some of them being
new species (Gramaccioli, Griffin and Mottana, 1980, 1982; Lucchetti,
Penco, Rinaldi, 1981; Basso, 1987). Recently, in a rock sample collected at
Gambatesa Mine (near Reppia, Val Graveglia) another new mineral, anorthorhombic manganese sulfite, was found.
Two synthetic compounds with this chemical composition are known:
the corresponding orthorhombic phase, the structural study of which has
been performed by means of X-ray and infrared analyses (Baggio and
Baggio 1976), and a monoclinic modification (Lutz, EI-Suradi and Engelev,
1977).
Up to now, the only two natural sulfites found were scotlandite, PbS03(Paar, Braithwaite, Chen and Keller, 1984; Sarp and Burri, 1984; Pertlik
and Zemann, 1985; Green, 1989), and hannebachite, CaS03' 1/2HzO(Hentschel, Tillmanns and Hofmeister, 1985).
The new mineral has been named gravegliaite from the valley so rich ofunusual minerals. The mineral and the name have been approved by the
IMA Commission on New Minerals and Mineral Names. Type material isdeposited in the collection of the Dipartimento di Scienze delia Terra,
Sezione di Mineralogia, U niversita di Genova.
Occurrence

and physical properties

The gravegliaite mineralization occurs at the surface of cavities along fractures crosscutting tephroite, bementite, braunite, hausmannite and hematite
bearing layers in the cherts (Diaspri of Mt Alpe Formation). In the same
fractures, but mainly in the siliceous layers, also chalcocite and rarely
alabandite are locally found.
This occurrence primarily leads to the question about the origin of thesulfur, which is lacking in the mineral phases of the manganesiferous layers.
Sulfide phases, mainly pyrite, are however common both in the stratigraphically underlying ophiolitic breccias and in the overlying pelitic levels(Calcari a Calpionella and Argille a Palombini Formations).
In the Ligurian ophiolitic sequences remobilization, by hydrous solutions, and redeposition of sulfides (mainly chalcopyrite and pyrite) constitute a very common feature that often gives rise to concentrations even of
economic interest (Cortesogno et aI., 1979). The wide range circulation ofsuch solutions, at low thermality (T < 200°C) and commonly SZ -enriched,-generally occurs along fractures formed during brittle, mainly tensional,
deformative phases, which arise after folding and metamorphic re-equilibration in the prehnite-pumpellyite facies.
Sulfites, intermediate phases between the more common sulfides andsulfates, are rarely observed in nature. Concerning gravegliaite, it can besupposed that, at the contact of the circulating SZ- -bearing brines with

Gravegliaite,

MnS03

Fig. 1. Gravegliaite. 3 H20, a new mineral from Val Graveglia

99

crystal aggregates.

MnH -, MnH -, FeH -mineral phases, takes place a redox reaction leading
to a precipitation of MnS03 . 3 H20. The sulfates, possibly formed during
this reaction, cannot precipitate owing to their higher solubility.
Gravegliaite appears as euhedral prismatic crystals elongated parallelto [010], up to 0.5 mm long, and as sheaf-like or radial aggregates (Fig. 1),
up to 0.2 mm in diameter. The mineral morphology is characterized by two
forms: a dominant prism {hOI} terminated by dipyramid. Very few crystals
show a pseudohexagonal habit possibly related to twinning. Gravegliaite
is colourless, with white streak and vitreous lustre, transparent and nonfluorescent. It presents cleavage parallel to [010] and no fracture.
The mineral is insoluble in water and in ethyl alcohol, soluble in strong
acids.
It is biaxial, nonpleochroic and shows strong dispersion. The refractive
indices, measured by Becke's method using Cargille's liquids (Na light at25'C), are: n~ = 1.590(2), nfJ= 1.596(2), ny = 1.636(2), Z = b. The mineralis optically positive and has an optical axial angle, measured by a five axes
universal stage, 2 Vy = 41::!::3° (2 Veale= 43°).
The density could not be measured, as other physical and chemical
properties, because of the small size and paucity of the crystals (deale =2.39 g' cm-3).
The internal consistence among the refractive indices, density andchemical composition, based on the Gladstone-Dale relationship, has beentested; the index (1 - KplKe) = 0.023 indicates an excellent compatibility(Mandarino,1981).

100

R. Basso, G. Lucchetti and A. PalenzonaTable 1. Chemical compositionof gravegliaite.

~

MnO
S02
Total
H20a
a

Range

Standard
deviation

Mean
wt%

Atoms numberson the basisof 6 oxygens

36.55 - 38.46

0.5
0.4

37.83
33.51
71.34
28.66

1.01
0.99

32.94-34.86

H20 wt% evaluated

6.02

as lOa-sum.

Chemical composition
Thirteen chemical analyses of three different crystals, obtained from theholotype specimen, were performed by means of a Philips SEM 515 electron
microscope equipped with an EDAX PV9100 in energy dispersive mode,with an accelerating voltage of 15 kV and beam current of about 2 nA. The. 6 HzO was used as standard
pure synthetic compound (NH4hMn(S04hfor both Mn and S. No other element was detected, except traces of Ca ina few cases. Spot analyses show neither compositional zoning in individual
crystals nor variation of composition among them over 5 (Jfor both MnOand SOz. Because of the paucity of the available mineral the water content
could not be measured experimentally, hence the value of HzO weightpercent, reported in Table 1, was calculated by difference.
The empirical formula obtained is very close to the ideal
MnS03 . 3 HzO, confirmed by the structural analysis.

X-ray powder diffraction

pattern

X-ray powder pattern was obtained by a Gandolfi camera using a Mnfiltered FeKa radiation. Relative intensities were assigned by visual estimate
and the reflections were indexed on the basis of the X-ray powder patterncalculated by the LAZY PULVERIX program (Yvon, ]eitschko andParthe, 1977). Input data of the calculated pattern were the ideal composition and space group, unit cell parameters, structural model and temperature factors according to X-ray single-crystal analysis. Scattering factors
for neutral atoms were used and anomalous dispersion correction wasapplied.
Unit cell parameters refined from powder data are: a = 9.762(8), b =5.639(4) and c = 9.564(9) A. In Table 2 the X-ray powder diffraction data
are shown. A few very weak reflections, in the range 1.056 < d < 1.512 A,
are not reported.

Gravegliaite,

MnS03. 3 H20,a new mineral

from

Table 2. X-ray powder diffraction
data of gravegliaite________.__..______.._____n.n_____'_'.____..___._________.__
h k I

101

Val Graveglia.------.-.---------'--,~.'--'---~

Calculated

Measured-_..---

d

1

h k I

(d in A).
Calculated

Measured-------------'--

--'-

d

d

1

d

1

1.851
1.836

VW
VW
VW

----.-------,---------_.._-

101
002
201
111
102
210
21 1
202
112
103
212
020
31 1
203
113
121
21 3
221
122
410
321
412
304
105

6.380
4.779
4.347
4.347
4.292
3.690
3.442
3.415
3.415
3.029
2.920
2.817
2.703
2.668
2.668
2.605
2.411
2.364
2.355
2.240
2.079
2.028
1.926
1.876

100
38
30
98
58
4
42
13
49
18
11
13
51
29
5
34
51
14
15
10
6
8
9
2

6.83
4.77

S
W

420
41 3

1.845
1.832

9
13

131

1.811

9

4.33

VS

3.69

VVW

3.43

VS

3.024
2.930
2.818
2.704

W
VW
VVW
M

2.666

M

2.605
2.414

W
M

j 2.362

W

2.244
2.080
2.028
1.929
1.877

VW
VVW
VW
VW
VVW

015
502
124
323
231
51 2
422
132
21 5
31 5
610
1 25
233
504
823
725
253
544
428
741

1.810
1.807
1.791
1.771
1. 724
1.721
1.721
1.721
1.697
1.582
1.563
1.561
1.536
1.512
1.056
1.046
1.038
1.031
1.003
0.986

7
1.812
4
29
1.790
6
1.772
3
10
1.726
7
13 J
1.703
7
3
1.586
2
1.562
6
9
1.537
8
1.512
3
1.056
1.046
3
6
1.039
9
1.030
10
1.003
19
0.987

}
}
]

-----,----

}

VW
VW
M
VW
VVW
VVW
VVW
VVW
VW
VW
VW
VW
W
W
.--

Crystal structure refinement
X-ray data collection was performed on a prismatic crystal with dimensions
0.292 mm x 0.125 mm x 0.063 mm by means of an Enraf-Nonius CAD-4
automatic single-crystal diffractometer. Cell dimensions were determined
and refined from 25 reflections with 19 < () < 22 degrees. The intensity data
were collected up to () = 30 degrees, using graphite monochromatized Moradiation and w-(J scan mode, and corrected for absorption (1pscan mode:
North, Phillips and Scott Mathews, 1968). The crystal structure was refinedin Pnma space group starting with the coordinates resulted from the structural analysis of the corresponding synthetic compound (Baggio and
Baggio, 1976). Eight cycles of least squares refinement were carried out by
a largely modified version of the ORFLS program (Busing, Martin andLevi, 1962), using the scattering factors for neutral atoms from the International Tables for X-ray Crystallography, Vol. IV. Total site occupancy
was fixed for Mn and S; scale factor, secondary extinction coefficient,coordinates and temperature factors were simultaneously derived. The
anisotropic temperature factors were introduced after the fourth cycle.

102

R. Basso, G. Lucchetti and A. Palenzona------------

Table 3. Crystal and X-ray data for gravegliaite.
---~--~~''---_.

MnS03 . 3 H20
4Pnma
9.763(1)5.635(1)9.558(1)

Idealized formula
Z
Space group
a (A)
b(A)
c (A)
Il(MoK.,

mm

-

1)

2.95
1641
829
594

Measured reflections
Independent reflections

Observed reflections J > 3 CJ(J)

0.036
0.058

R (observed)
R (all)Extinction parameter--'---~-'-"---"

Table 4. Atomic coordinates
1959) for gravegliaite.
Atom

x/a

and equivalent

0.2236(1)0.9344(2)0.0892(4)0.1185(3)0.3686(5)0.3638(3)isotropicy/h---._---_.---._---._------_.---

Mn
S
01
02
03
04

6.5(9) x 10- 4

temperaturefactors (Hamilton,z/c

BH (A 2)0.0622(1 )0.9099(2)0.8824(5)0.1716(3)0.2367(5)0.9507(3)

1.17
1.01
2.03
1.85
2.28
1.41

------

0.25
0.25
0.25
0.5348(6)0.25
0.5056(6)---,.----

Tables 3, 4 and 5 summarize experimental
crystal structure refinement. 1

details and results of theDiscussion
The crystal structure refinement confirms gravegliaite to be the natural
analogue of the orthorhombic MnS03 . 3 H20 studied by Baggio and
Baggio (1976).
According to the description of the structure of these authors, theatomic framework of gravegliaite may be outlined as consisting of slabs
running indefinitely along [010]. Each slab is made by a pair of infinite
linear sequences, linked together by bridging sulphur atoms, of isolated
Mn octahedra. Projecting the structure down h axis, each slab may be
1 Additional material to this paper can be ordered referring to the no. CSD 55015,
names of the authors and citation of the paper at the Fachinformationszentrum
EnergiePhysik-MathematikGmbH, W-7514 Eggenstein-Leopoldshafen
2, FRG.

Gravegliaite,

MnS03. 3 H20, a new mineral from Val Graveglia

103

Table 5. Selected interatomic distances (A) and angles n in gravegliaite.
Mn-01
2 Mn - 02
Mn-03
2 Mn-04
Average

2.162(4)2.173(3)2.187(4)2.255(3)2.201

2 01-022 01-04
02 - 02'2 02-03
2 02 - 04
04 - 04'
Average

3.209(5)
3.113(4)3.210(7)2.987(4)3.197(4)3.090(5)2.881(6)3.107

2 01-Mn-022-04
02-Mn-02'
2 02-Mn-03
2-04
2 03-Mn-04
04-Mn-04'
Average95.50(10)89.58(11)95.24(17)86.49(11 )92.42( 11)88.14(12)79.40(15)89.91

2 03 - 04

Symmetry code: (') = x, 1/2 - y, z;

S-01
2 S-02Average

1.535(4)1.531 (3)1.532

2 01-02
02 - 02"
Average

2.419(4)2.425(6)2.421

2 01-S-02
02-S-02"
Average104.18(16)1 04.

7 5(25)104.37n = x, 3/2 - y, z.

schematically depicted by a parallelogram representing the contour line of
the section orthogonal to [010]. The short sides of parallelograms are nearlyparallel to [001], the long ones are alternately quasi-parallel to [401] or[40f] (Fig. 2). Since only hydrogen bonds seem to play the role of linking
neighbouring slabs, in agreement with observed cleavage parallel to [010],
an attempt to localize the hydrogen atoms has been made. Some difficulties
arose for distinguishing noise from true H peaks using a conventional
difference synthesis. Therefore difference maps, calculated removing highangle reflections, and Fourier maps were also used to improve the chancesof finding H atoms (Teller, Bau and Gutlich, 1981).
H3A at 0.445, 0.25, 0.294 and H3B at 0.284, 0.25, 0.305 can be reasonably assumed as the hydrogen atoms forming with 03 oxygen atom one of
the water molecules of gravegliaite. The values of 03 - H3A (0.93 A), 03-

H3B (1.05 A), H3A - H3B (1.58 A) distances and ofH3A - 03~

H3B angle(105.4°) agree with the common geometry of water molecule in crystalline
hydrates.

From 03 two shorter inter-slab 0 - 0 distances, 03 - 02 (3.050 A) and
03 -04 (3.351 A), both repeated by mirror plane, were considered forpossible weak and bifurcated hydrogen bonds involving H3A and H3B,
respectively. The 02 atom, whose position relative to the 03( donor) - H3A

104

R. Basso, G. Lucchetti and A. Palenzona~--------

"

03

04

fSJ 0
Mn

°75

Mn
0.25

04

02

01
:,1

. 75
S

;"H3A ":01
''

03

~5.

L5l 0
03//

04

H4A

'

!SJ
Mn

075

".02

03

04

.H38

~~,

Mn
25'

//

04

02

03

011"'~5~'ac2//.~5'01
03
Mn
°75

03

151
04

Fig. 2. Schematic picture of gravegliaite

03

structure,04-

view along [010].

bond leads to the H3A... 02 distance of 2.36 A and to the 03 - H3A. . .02

angle of 131S', is expected to act as an acceptor oxygen according to Brown(1976). On the contrary it is hard to establish whether interaction, to beconsidered a hydrogen bond, takes place between 03 and 04, on accountof the very long distances 03 -04 and H3B... 04 (2.43 A) and the large
angular value 03 - H3B... 04 = 145.10 (Brown, 1976).
Regarding the other water molecules, H4A at 0.358, 0.505, 0.859 givesa slightly short 04 - H4A distance (0.88 A).
The shortest inter-slab 04 - 02 distance (2.683 A), the H4A... 02 (acceptor) distance (1.82 A) and the nearly linear bond 04 - H4A... 02 angle(167.1) delineate a good geometry for a strong hydrogen bond (Brown,1976).
Great difficulties were encountered to determine a reasonably certain
position of the second hydrogen atom (H4B) bonded to 04 and consequently to ascertain whether the two short 04 - 04 distances, an intra-slab
one of 2.754 A (not octahedral edge) and another inter-slab of 2.822 A,
indicate interactions between pairs of equivalent 04 oxygens to assign tohydrogen bonds. In such a case 04 would act as donor and acceptor oxygenat the same time.
On the basis of the available data a suggestive hypothesis could be tosuppose a hydrogen atom delocalized between at least two positions nearGravegliaite,

MnS03. 3 H20. a new mineral from Val Graveglia'

105'.'---

Table 6. Empirical bond valences for gravegliaite.
-_.------------

Mn

S

H3A

1.34
1.36
(0.01 )

0.08
0.84

H3B

H4A

H4B

L

1.00

1.71
2.01
2.18
2.07

~.--_._-------

01
02
03
04

0.37
0.36
0.34
0.28

0.21
1.00
0.79

---,

~

to a pair of weak peaks in the difference Fourier map (0.358, 0.644, 0.950
and 0.428, 0.515,0.982).
These positions are 0.78 A and 0.70 A from the

04 donor oxygen, respectively. Such hypothesis accounts for two facts:

both 04 - 04 distances, above reported, are well within the range forhydrogen bonds; a hydrogen atom totally assigned to the position suitableto bond the two equivalent 04, pertaining to different slabs (inter-slabbond), infers a too short H - H distance because of the presence of theinversion center. On the other hand this interaction yields an appreciable
contribution to the cohesion of the structure.
Unfortunately the bond valence table for gravegliaite, that clearly shows
03 and 04 to be oxygen atoms of water molecules, is not helpful to remove
the uncertainties about the doubtful hydrogen bonds and the possible
interaction between Sand 03 (S-03= 4.438 A) suggested by Baggio
and Baggio (1976), because the bond valence contributions involved are
negligible owing to the empirical procedure of the estimate.
The bond-valence calculation (Table 6) was carried out using the curvesof Brown and Altermatt (1985) for manganese, sulphur and oxygen atoms.
According to these authors the H... 0 (acceptor) bond valence has been
estimated as a function of the 0 - 0 distance and consequently the (donor)
O-H valence by subtracting the sum of the H..O (acceptor) valences from
1.0. In agreement with the previous considerations H3B was not considered
as involved in hydrogen bond.
Acknmvlcdgmcnt.
Istruzione.

This study was supportedby the Italian

Ministerodella Pubblica

References
Baggio, R. F.. Baggio, S.: Crystal structure and chemical bonding of manganese(lI)sulphite trihydrate. Acta Crystallogr. B32 (1976) 1959 -1962.
Basso. R.: The crystal structure of palenzonaite,a new vanadate garnet from Val
Graveglia (Northern Apennines, Italy). Neues Jahrb. Mineral. Monatsh. (1987)
136-144.
Brown, I. D.: On the geometry of 0 - H... 0 hydrogen bond. Acta Crystallogr. A32(1976) 24-31.
Brown, I. D., Altermatl. D.: Bond-valence parameters obtained from a systematic analysis of the inorganic crystal structure database. Acta CrystaJlogr. B41 (1985) 244247.

106

R. Basso, G. Lucchetti and A. Palenzona~~----_._--_.---

Busing, W. R., Martin, K. 0., Levi, H. A.: ORFLS, a FORTRAN crystallographic leastsquares refinement program. U.S. Natl. Tech. Inform. Servo ORNL-TM-305(1962).
Cortesogno, L., Lucchetti, G., Penco, A. M.: Le mineralizzazioni a manganese nei diaspridelle ofioliti liguri: mineralogia e genesi. Rend. Soc. It. Mineral. Petrol. 35 (1979)
151-197.
Gramaccioli, C. M., Griffin, W. L., Mottana, A.: Tiragalloite, Mn4[AsSi3012(OH)],a
new mineral and the first example of arsenatotrisilicate.
Am. Mineral. 65 (1980)
947-952.
Gramaccioli, C. M., Griffin, W. L., Mottana, A.: Medaite, MndVSis01s(OH)],a newmineral and the first example of vanadopentasilicate
ion. Am. Mineral. 67 (1982)
85-89.
Green, D. I.: Scotlandite from Higher Roughton Gill, Caldbeck Fells, Cumbria. Mineral.
Mag. 53 (1989) 653.
Hamilton, W. c.: On the isotropic temperature factor equivalent to a given anisotropic
temperature factor. Acta Crystallogr. 12 (1959) 609-610.
Hentschel, G., Tillmanns, E., Hofmeister, W.: Hannebachite, natural calcium sulfite hemihydrate, CaS03 . 1/2 H20. Neues Jahrb. Mineral. Monatsh. (1985) 241 - 250.
Lucchetti, G., Cortesogno, L., Palenzona, A.: Low-temperature
metamorphic mineral
assemblages in Mn - Fe ores from Cerchiara Mine (Northern Apennine, Italy). Neues
Jahrb. Mineral. Monatsh. (1988) 367 - 383.
Lucchetti, G., Penco, A. M., Rinaldi, R.: Saneroite, a new natural hydrate Mn-silicate.
Neues Jahrb. Mineral. Monatsh. (1981) 161-168.
Lutz, H. D., El-Suradi, S., Engelev, B.: Zur Kenntnis der Sulfite und Sulfithydrate derzink-, mangan-, magnesium- und cobalt-rontgenographischen,spektroskopischen
und thermoanalytischen
Untersuchungen.
Z. Naturforsch. B32 (1977) 1230-1238.
Mandarino, J. A.: The Gladstone-Dalerelationship: part IV. The compatibility concept
and its applications. Can. Mineral. 19 (1981) 441-450.
North, A. C. T., Phillips, D. c., Scott Mathews, F.: A semiempirical method of absorption
correction. Acta Crystal1ogr. A24 (1968) 351-359.
Paar, W. H., Braithwaite, R. S., Chen, T. T., Keller, P.: A new mineral, scotlandite(PbS03), from Leadhills, Scotland; the first naturally occurring sulphite. Mineral.
Mag. 48 (1984) 283-288.
Pertlik, F., Zemann, J.: The crystal structure of scotlandite, PbS03. Tschermaks Mineral.
Petro gr. Mitt. 34 (1985) 289-295.
Sarp, H., Burri, G.: Seconde occurrence du nouveau mineral scotlandite PbS03. Schweiz.
Mineral. Petrogr. Mitt. 64 (1984) 317 - 321.
Teller, R. G., Bau, R., Gutlich, P.: Structure and bonding - Metal complexes. Vol. 44,
p. 1-82, Berlin, Heidelberg, New York: Springer-Verlag 1981.
Yvon, K., Jeitschko, W., Parthi:, E.: LAZY PULVERIX, a computer program, forcalculating X-ray and neutron diffraction powder patterns. J. Appl. Crystallogr. 10(1977) 73 - 74.