Eur. J. Mineral.
2012, 24, 1061–1067
Published online June 2012

Paseroite, PbMn2þ(Mn2þ,Fe2þ)2(V5þ,Ti,Fe3þ,&)18O38, a new member of thecrichtonite group
STUART J. MILLS1,2,*, LUCA BINDI3, MARCELLA CADONI4, ANTHONY R. KAMPF2, MARCO E. CIRIOTTI5
and GIOVANNI FERRARIS4
1

Geosciences, Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard,
Los Angeles, CA 90007, USA*Corresponding author, e-mail: smills@museum.vic.gov.au
3
Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, I-50121 Firenze, Italy
4
Dipartimento di Scienze della Terra, Università degli Studi di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy
5
Associazione Micromineralogica Italiana, via San Pietro 55, I-10073 Devesi-Ciriè, Torino, Italy
2

Abstract: Paseroite, ideally PbMn2þ(Mn2þ,Fe2þ)2(V5þ,Ti,Fe3þ,&)18O38, is a new mineral (IMA2011-069) from fossil wood in the upper
part of the Molinello mine, Val Graveglia, Italy. Paseroite occurs in direct association with quartz, chalcocite, volborthite, metatyuyamunite
and pyrophanite, and was also found as zones within V-rich senaite crystals with which it forms a solid-solution series. Paseroite forms as
isolated submetallic, dark grey to black, elongated scalenohedral crystals between 50 and 100 mm in length, with the forms {001} and {102}present. The tenacity is brittle, the fracture conchoidal, and the streak is black. The Vickers hardness is 847 kg mm2 (load 500g), which isequivalent to 6–6.5 on the Mohs scale. The calculated density is 4.315 g/cm3 (on the basis of the empirical formula). In plane-polarised
incident light, paseroite is greyish in colour, weakly bireflectant and non-pleochroic. Internal reflections are absent. Between crossed polars,
paseroite is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) are: 18.4 %, 18.2 % (471.1 nm); 17.9%, 17.7 % (548.3 nm); 17.6 %, 17.3 % (586.6 nm); and 17.0 %, 16.8 % (652.3 nm), respectively. The empirical formula, calculated on thebasis of 38 O atoms pfu is: (Pb0.61Sr0.39)1.00 (V5þ7.78Ti4þ7.03Mn2þ1.86Fe2þ0.67Fe3þ0.37Zn0.24Na0.19U0.02Mg0.02&2.82)21.00O38. According
to the structural results, the simplified formula is: PbMn2þ(Mn2þ,Fe2þ)2(V5þ,Ti,Fe3þ,&)18O38. Structurally, paseroite crystallises in thespace group R3, with the unit-cell parameters a ¼ 10.3894(5), c ¼ 20.8709(8) Å, V ¼ 1950.98(15) Å3 and Z ¼ 3. The crystal structure wasrefined to R ¼ 0.0234 for 632 reflections with Io . 2s(Io) and is isostructural with senaite and all other members of the crichtonite group.
The eight strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.417 (100) (024), 3.012 (21) (300), 2.896 (61) (216), 2.858 (36)(214), 2.765 (27) (303), 2.260 (85) (144), 2.149 (65) (415) and 1.809 (57) (418). The name is after Marco Pasero (b. 1958), Professor of
Mineralogy at the University of Pisa.
Key-words: paseroite, senaite, crichtonite group, crystal structure, vanadium, new mineral, solid solution, Molinello,
Val Graveglia, Italy.

1. Introduction

Paseroite is named for Marco Pasero (b. 1958),
Professor of Mineralogy at the University of Pisa, Italy,
in honour of his contributions to mineralogy and crystallography in general, and especially in recognition of his
contributions to Italian mineralogy. Professor Pasero is a
co-author of the book Italian Type Minerals (Ciriotti et al.,2009) and has described 12 new minerals from Italy,
including two new members of the crichtonite group, dessauite-(Y) and gramaccioliite-(Y). He has also acted as themember for Italy on the IMA Commission on New
Minerals, Nomenclature and Classification (CNMNC)
and is currently the Vice-Chairman. The mineraland name (IMA2011-069) were approved by the
IMA–CNMNC prior to publication. Co-type material isdeposited in the mineralogical collections of the Museo

A sample of fossilised wood collected by S. Bottoni, S.
Camarda and G. Sanguineti from the upper part of theMolinello mine (Val Graveglia, Italy), has yielded aremarkable association of minerals, including: chalcocite,
hummerite, lenoblite, metatyuyamunite, pyrophanite,
quartz, roscoelite, santafeite, tangeite and volborthite.
Also found in this assemblage are two members of thecrichtonite group, V-rich senaite and the new V-dominant
member named paseroite; the latter is the subject of thepresent study. Both paseroite and V-rich senaite were firstobserved by Giuseppe Finello. Additional phases, including some potentially new minerals, are also part of thisassemblage and are currently under investigation.
eschweizerbart_xxx

0935-1221/12/0024-2243 $ 3.15
DOI: 10.1127/0935-1221/2012/0024-2243# 2012 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart

1062

S.J. Mills, L. Bindi, M. Cadoni, A.R. Kampf, M.E. Ciriotti, G. Ferraris

di Storia Naturale, Sezione di Mineralogia e Litologia,
Firenze, catalogue number 3111/I, and in the mineralogicalcollections of the Museo Regionale di Scienze Naturali,
Torino, catalogue number 15900.

The density of paseroite could not be measured because ofsmall grain size and the strong zoning observed in most of thecrystals. The calculated density (on the basis of the empiricalformula and single-crystal unit cell) is 4.315 g/cm3.

2. Occurrence, location and physical properties 3. Optical properties
The Molinello mine is located on the left bank of the Rio
Novelli, Val Graveglia, Ne, Genoa Province, Liguria, Italy,
and is the type locality for six other mineral species(Ciriotti et al., 2009; Bindi et al., 2011). Paseroite wasfound in microcavities and fractures in a piece of fossilised
wood trunk (genus Araucariaceae; Cortesogno & Galli,1974), measuring 50  100 cm, which was found partially embedded in grey chert. The new mineral is commonly found in direct association with quartz, chalcocite
and volborthite, and more rarely with metatyuyamunite
and pyrophanite. The presence of several V5þ minerals inassociation with paseroite, and the presence of uranium,
indicates oxidising conditions of formation (e.g. Drever,1997). We note that volborthite can be synthetically prepared at room temperature with a pH of 3 (Melghit et al.,2003), or at a pH 6 if the temperature is 100  C (Melghit,2006) and thus this may give insight into the formation
conditions needed to produce paseroite.
Paseroite occurs as submetallic, dark grey to black,elongated scalenohedral crystals between 50 and 100 mm
in length. Crystals are usually isolated and may be zoned
between paseroite and V-rich senaite. The main forms
observed are {001} and {102}. The tenacity is brittle, thefracture conchoidal, and the streak is black. The Vickers
hardness of paseroite is 847 kg mm2 (load 500 g), with arange (10 measurements) of 834–865 kg mm2, which isequivalent to 6–6.5 on the Mohs scale.

In plane-polarised incident light, paseroite is greyish incolour, weakly bireflectant and non-pleochroic. Internalreflections are absent. Between crossed polars, paseroite
is anisotropic, without characteristic rotation tints. The
reflectance was measured in air by means of an MPM200 Zeiss microphotometer equipped with a MSP-20 system processor on a Zeiss Axioplan ore microscope. The
filament temperature was approximately 3350 K. Readings
were taken for specimen and standard (SiC) maintained
under the same focus conditions. The diameter of the circular measuring area was 0.1 mm. Reflectance percentages(Rmin and Rmax) are: 18.4 %, 18.2 % (471.1 nm); 17.9 %,17.7 % (548.3 nm); 17.6 %, 17.3 % (586.6 nm); and 17.0 %,16.8 % (652.3 nm), respectively. By analogy with senaite,
paseroite may be uniaxial (–).

4. Chemical composition
The chemical composition of the paseroite crystal used forthe structural study was determined by WDS methods
using a JEOL JXA-8200 electron microprobe. Major andminor elements were determined at an accelerating voltage
of 20 kV, a 30 nA beam current, a beam size of 2 mm, andwith 40 and 20 s counting time on the peak and background, respectively. The crystal fragment was found to
be relatively homogeneous (Fig. 1, Table 1); however,Fig. 1. Backscattered electron (top) and elemental X-ray maps (bottom) for the paseroite crystal used in the chemical and crystal structure studies.
eschweizerbart_xxx

Paseroite, a new member of the crichtonite group

1063

Table 1. EMPA WDS analyses of paseroite (11 analyses).
Oxide

wt%

Range

SD

Probe standard (line)

Na2O
MgO
MnO
ZnO
SrO
PbO
FeOa
Fe2O3a
La2O3
Ce2O3
TiO2
ThO2
UO3
V2O5
Total

0.35
0.05
7.70
1.15
2.36
8.01
2.80
1.71
0.02
0.03
32.78
0.05
0.36
41.27
98.64

0.28–0.42
0.02–0.08
7.55–7.81
1.07–1.21
2.20–2.45
7.88–8.19

0.05
0.02
0.25
0.07
0.11
0.31

0.00–0.04
0.00–0.07
32.13–32.98
0.01–0.08
0.27–0.46
40.90–41.60

0.01
0.02
0.52
0.01
0.04
0.47

Albite (Ka)
Diopside (Ka)
Bustamite (Ka)
Willemite (Ka)
Strontianite (Ka)PbSO4 (La)
Hematite (Ka)
Hematite (Ka)
La3ReO8 (La)Monazite (La)
Rutile (Ka)Thorianite (Ma)Uraninite (Ma)
LaVO4 (Ka)a

Allocated based on site distributions. FeOtot ¼ 5.13 wt%.
Table 2. Powder X-ray diffraction data for paseroitea.

other crystals examined ranged between V-rich senaite
and paseroite. Nb, Y, Cr and Ba were analysed for, butwere below the detection limits. The mean results of
11 analyses are given in Table 1. Vanadium wasassumed to be pentavalent and Mn divalent based on
the association with other V5þ and Mn2þ minerals andbecause of the presence of a stoichiometric formulaand a total which approaches 100 wt%. If V wasassumed to be trivalent, the average analytical total
would be 92.57 wt%. The structure confirms thelack of water in the structure (see below), and thus
we can be quite confident of the site assignments.
Unfortunately due to lack of material we were unable
to undertake advanced spectroscopic methods on
paseroite. We were also unable to obtain a spectrum
using Raman spectroscopy.
The empirical formula, calculated on the basis of 38 O
atoms pfu (consistent with members of the crichtonite
group) is: (Pb0.61Sr0.39)1.00(V5þ7.78Ti4þ7.03Mn2þ1.86
Fe2þ0.67Fe3þ0.37Zn0.24Na0.19U0.02Mg0.02&2.82)21.00O38(with þ0.02 charge due to rounding errors). Taking into
account the crystal structure, the simplified formula is:PbMn2þ(Mn2þ,Fe2þ)2(V5þ,Ti,Fe3þ,&)18O38.

5. Powder X-ray diffraction
Powder X-ray diffraction data for paseroite were obtainedon a Rigaku R-Axis Rapid II curved–imaging-plate microdiffractometer utilising monochromatised MoKa radiation.
Observed d spacings and intensities were derived by profile fitting using JADE 9.3 software (Materials Data Inc.).
Data (in Å) are given in Table 2. Hexagonal unit-cellparameters refined from the powder data using JADE 9.3
with whole-pattern fitting are a ¼ 10.434(1), c ¼ 20.895(2)Å, V ¼ 1970.29(2) Å3 and Z ¼ 3, which are in good
agreement with those obtained from the single-crystal
study (see Section 6).

dobs

Iobs

Icalc

dcalc

h

k

l

5.215
4.415
4.146
3.792
3.417
3.068
3.012

7
9
9
13
100
19
21

2.896
2.858
2.834

61
36
7

2.765

27

2.644
2.608

15
8

2.488

4

2.443
2.437

16
4

2.260

85

2.149
2.121
1.972
1.927
1.919
1.809
1.783

65
7
7
8
5
57
6

1.716

17

15
17
23
19
100
20
46
49
51
62
13
35
27
17
16
15
16
6
17
14
14
39
22
6
59
12
10
14
11
54
9
9
14

5.195
4.398
4.131
3.787
3.407
3.060
2.999
2.890
2.890
2.849
2.830
2.754
2.754
2.637
2.637
2.597
2.478
2.478
2.433
2.433
2.427
2.251
2.251
2.142
2.142
2.118
1.963
1.919
1.914
1.803
1.779
1.710
1.710

1
0
2
0
0
2
3
1
2
2
1
0
3

1
1
2
1

1
4
2
4
1

1
3
4
2
4
3
1
4
3

1
4

1
2
0
1
2
0
0
1

1
1
0
3
0
3
2
2
3
4

2
2

1
3
4
1

1

1
1
2
3

1

1
5
1

0
1
2
5
4
5
0
6
6
4
7
3
3
5
5
0
1
1
3
3
2
4
4
5
5
9
0
4
7
8
10
6
6

a

Only reflections with Icalc . 5s(Icalc) are listed.

6. Single-crystal X-ray diffraction
The X-ray data collection was performed on the same
crystal used for the electron-microprobe study using aneschweizerbart_xxx

1064

S.J. Mills, L. Bindi, M. Cadoni, A.R. Kampf, M.E. Ciriotti, G. Ferraris

Table 4. Tentative site-distribution scheme for paseroite.

Oxford Diffraction Xcalibur 3 CCD diffractometer, utilising graphite-monochromatised MoKa radiation (l ¼0.71073 Å). Experimental details of the data collection
are reported in Table 3. The structure was solved bydirect methods using SHELXS-97 (Sheldrick, 2008)
and the location of all atoms was straightforward.
SHELXL-97 (Sheldrick, 2008) was used for the refinement of the structure. The hexagonal setting was used forthe refinement of the data. We note that several refinements are reported in the rhombohedral setting for members of the crichtonite group; however, the ICSD
database has transposed these to the standard hexagonalsetting. We refined the dominant atomic species versus
vacancy at each structural site to obtain a mean electron
number. The final solution was checked by PLATON(Spek, 2009).
The crichtonite structure (see below) has six cation sites.
From the crystal-structure refinement and the electronmicroprobe data (above), a tentative site-distribution
scheme can be proposed (Table 4), which takes into
account the common elements found on each of thesesites and which is consistent with that reported for crichtonite and senaite (Grey et al., 1976). A summary of theseelements, modified from Wülser et al. (2005), can be foundin Table 5. It is only possible to give a definitive scheme for
the M0, M1 and M2 structural sites, while the M3, M4 andSiteseEPMAeX-rayM0: (Pb0.61Sr0.39)
M1: (Mn2þ0.79Zn0.19U0.02)
M2: (Mn2þ0.54Fe2þ0.34Na0.09Zn0.03Mg0.01)
M3þM4þM5: (V5þ7.78Ti4þ7.03Fe3þ0.37&2.82)

64.8
27.3
23.2
343.2

63.9
27.3
20.8
351.6

M5 octahedral sites were considered together because of
the close scattering powers of Ti and V.
The tentative site-distribution scheme gives the following structural formula for paseroite: M0(Pb0.61Sr0.39)
M1(Mn2þ0.79Zn0.19U0.02)1.00M2(Mn2þ0.54Fe2þ0.34
1.00
Na0.09Zn0.03 Mg0.01)1.00M3,M4,M5(V5þ7.78Ti4þ7.03Fe3þ0.37&2.82)18.00 O38.
The final refinement converged to R1 ¼ 0.0234 [632reflections with Io . 2s(Io)] and the resulting atomic parameters and displacement factors are listed in Tables 6 and 7,
and bond lengths in Table 8. The residual highest peak anddeepest hole are: 1.23 and 1.27 e/Å3; both are close to
M0 and likely are related to some disorder in the position of
Pb and Sr, i.e. the two cations are not likely to be in exactly
the same position.

7. Description of the crystal structure anddiscussion
Table 3. Crystal data and structure refinement for paseroite.
Simplified formula

2þ

2þ

2þ

5þ

The minerals of the crichtonite group crystallise in the spacegroup R3. Their chemical composition is represented by thegeneral formula XIIAVIBIVT2VIC18O38, where the Roman
numerals preceding each component indicate the coordination numbers of their sites and: A ¼ Ba, K, Pb, Sr, La, Ce, Naor Ca; B ¼ Mn, Y, U, Fe, Zr or Sc; T ¼ Fe, Mn, Mg or Zn;
and C ¼ Ti4þ, Fe3þ, Cr, Nb, V5þ, Mn3þ or Al (e.g. Grey &Lloyd, 1976; Grey et al., 1976; Orlandi et al., 1997; Wülser
et al., 2005; Table 5). The cation sites are denoted asfollows: A ¼ M0, B ¼ M1, C ¼ M3 þ M4 þ M5 þ M6
and T ¼ M2. The four sites M3–M6 are grouped together
under C, because the cations which occupy them have very
similar ionic radii (rV5þ ¼ 0.54 vs. rTi4þ ¼ 0.605 Å;
Shannon, 1976).
The structure is defined by layers of close-packed octahedra (M1, M3, M4, M5 and M6) and tetrahedra (M2) andcontaining large 12-coordinated M0 sites (Fig. 2). The
octahedral site M6 shares a face with the tetrahedral siteM2, so that adjacent M2 and M6 sites cannot both beoccupied at the same time. The M2 site has been reported
as having a low occupancy in mathiasite (Gatehouse et al.,1983) and dessauite-(Y) (Orlandi et al., 1997). In thedessauite-(Y) structure, additional low-occupancy sites,labelled M7, M8 and M9, have also been reported. The
dominant A, B, C and T cations in the different sites
determine the mineral species. The following species
have been described thus far (cf. Theye et al., 2010 and
Table 5): cleusonite, crichtonite, davidite-(La), davidite-(Ce),3þ

PbMn (Mn ,Fe )2(V ,Ti,Fe ,&)18O38

Temperature
296(2) K
Wavelength
0.71073 Å
Space group
R3
Unit-cell dimensions a ¼ 10.3894(5) Åc ¼ 20.8709(8) Å
Volume1950.98(15) Å3
Z3
Density (calculated) 4.297 g/cm3
Absorption
3.388 mm1
coefficientF(000)
590
Crystal size
65  45  30 mm3
Theta range for data 8.15–34.98
collection
Index ranges
16h16, 16k16, 33l33
Independent
632 [Rint ¼ 0.070]
reflections
Refinement method Full-matrix least-squares on F2
Data/restraints/
632/0/99
parameters
Goodness-of-fit on F2 0.908
Final R indicesR1 ¼ 0.0234, wR2 ¼ 0.0268[I.2s(I)]R indices (all data)
R1 ¼ 0.0502, wR2 ¼ 0.0505
Extinction
0.00107(5)coefficient
Largest diff. peak
1.23 and 1.27 e/Å3
and holeeschweizerbart_xxx

Paseroite, a new member of the crichtonite group

1065

Table 5. Distribution of cations in the metal sites of crichtonite-group minerals (after Wülser et al., 2005).

Landauite
Loveringite
Lindsleyite
Mathiasite
Davidite-(La)Davidite-(Ce)Crichtonite
Dessauite-(Y)SenaiteGramaccioliite-(Y)Cleusonite
Paseroite

M0

M1

M2

M3–5

Reference

Na,Pb
Ca,LREE
Ba,K
K,Ba,Sr
La,Ce,Ca
Ce,La
Sr,Ba,Pb
Sr,Pb
Pb,Sr
Pb,Sr
Pb,Sr
Pb,Sr

Mn,Y
Zr,Fe
Zr,Fe
Zr,Fe
Y,HREE,U
Y,HREE,U
Mn
Y,U
Mn
Y,Mn
U
Mn

Zn2
(Mg,Fe)2(Mg,Fe)2(Mg,Fe)2(Fe,Mg)2(Fe,Mg)2(Fe,Zn)2(Fe,Zn)2(Fe,Zn)2(Fe,Zn)2(Fe,Zn)2(Mn,Fe)2

Ti,Fe,Nb
Ti,Fe,Cr,Al
Ti,Cr,Fe
Ti,Cr,Fe
Ti,Fe,Cr,V
Ti,Fe,Cr,V
Ti,Fe
Ti,Fe
Ti,Fe
Ti,Fe
Ti,Fe
V,Ti,Fe

Grey and Gatehouse (1978)
Gatehouse et al. (1978)
Zhang et al. (1988)
Gatehouse et al. (1983)
Gatehouse et al. (1979)
Gatehouse et al. (1979)
Grey et al. (1976)
Orlandi et al. (1997)
Grey et al. (1976)
Orlandi et al. (2004)
Wülster et al. (2005)
This paper

Table 6. Atoms, multiplicity and Wyckoff letter, fractional atom coordinates and equivalent isotropic displacement parameters (Å2) for
paseroite.
Atom

Wyckoff

x

y

z

Uiso

M0
M1
M2
M3
M4
M5
O1
O2
O3
O4
O5
O6
O7

3a
3b
6c
18f
18f
18f
18f
18f
18f
18f
18f
18f
6c

0
0
0
0.18510(7)0.08385(7)0.07595(8)0.1333(3)0.7109(3)0.3616(3)0.5930(3)0.0525(3)0.3653(3)00000.04422(7)0.33987(7)0.31544(7)0.1888(3)0.2050(3)0.1020(3)0.0332(3)0.8531(3)0.0985(3)00½0.31037(4)0.16498(3)0.60882(3)0.38897(3)0.5585(1)0.4465(1)0.5572(1)0.5480(1)0.3363(1)0.3386(1)0.2133(2)0.0240(1)0.0167(3)0.0171(3)0.0149(2)0.0165(2)0.0166(2)0.0208(4)0.0199(4)0.0221(5)0.0206(4)0.0214(5)0.0200(4)0.0158(6)Table 7. Anisotropic displacement parameters (Å2) for paseroite.
Atom

U11

U22

U33

U12

U13

U23

M0
M1
M2
M3
M4
M5
O1
O2
O3
O4
O5
O6
O7

0.0239(2)0.0169(4)0.0170(3)0.0151(3)0.0174(3)0.0169(3)0.019(1)0.020(1)0.021(1)0.021(1)0.020(1)0.022(1)0.016(1)0.0239(2)0.0169(4)0.0170(3)0.0152(3)0.0164(3)0.0164(3)0.024(1)0.019(1)0.022(1)0.018(1)0.017(1)0.020(1)0.016(1)0.0241(2)0.0164(5)0.0174(5)0.0148(3)0.0164(3)0.0168(3)0.0184(9)0.0212(9)0.0230(9)0.0208(9)0.026(1)0.0198(8)0.015(1)0.01194(8)0.0085(2)0.0085(2)0.0079(2)0.0090(2)0.0084(2)0.0103(9)0.0105(8)0.011(1)0.0083(9)0.0077(9)0.011(1)0.0081(5)0000.0003(2)0.0002(2)0.0001(2)0.0007(8)0.0006(7)0.0014(8)0.0003(7)0.0009(8)0.0015(8)00000.0005(2)0.0002(2)0.0001(2)0.0008(7)0.0016(7)0.0003(8)0.0001(8)0.0021(8)0.0003(7)0dessauite-(Y), gramaccioliite-(Y), landauite, lindsleyite,
loveringite, mathiasite and senaite.
The crystal structure of paseroite is consistent with thatreported for senaite and crichtonite by Grey et al. (1976)
and Grey & Lloyd (1976) and senaite by Armbruster &Kunz (1990). Its structure is dominated by a close-packed
anion framework with a nine-layer chhchh... stacking
sequence (Fig. 3). Large cations (Pb2þ, Sr2þ) replace O
at the origin of the unit cell and perturb this layer sequence(e.g. Fig. 2a and j). In the structure of paseroite, no extra
eschweizerbart_xxx

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S.J. Mills, L. Bindi, M. Cadoni, A.R. Kampf, M.E. Ciriotti, G. Ferraris

Table 8. Main interatomic distances (Å) and geometric parameters
for paseroite.
M0-O6 (6)
M0-O2 (6)

2.851(2)2.860(2)M1-O1 (6)
Voct
s2
l

2.131(2)12.90
0.20
1.0001

M2-O5 (3)
M2-O7
Mean
Vtet
s2
l

1.937(2)2.026(3)
1.959
3.85
11.89
1.0029

M3-O4
M3-O4
M3-O3
M3-O2
M3-O7
M3-O2
Mean
Voct
s2
l

1.919(2)1.956(2)1.957(2)1.975(2)2.011(2)2.020(3)
1.973
10.10
32.37
1.0095

M4-O6
M4-O2
M4-O3
M4-O6
M4-O5
M4-O1
Mean
Voct
s2
l

1.858(3)1.862(3)1.994(3)2.094(3)2.121(3)2.153(3)
2.014
10.63
56.45
1.0198

M5-O5
M5-O6
M5-O1
M5-O5
M5-O4
M5-O3
Mean
Voct
s2
l

1.868(3)1.931(3)2.016(3)2.023(3)2.045(3)2.054(3)
1.990
10.40
21.41
1.0075which resulted in an extra octahedrally-packed unit within
the cell.
For paseroite, both the EMPA and structure refinementshow the sum of A þ B þ T þ C cations to be substantiallylower than the ideal value of 22 pfu required by the formula
XII VIA B IVT2VIC18O38. Indeed, the structure refinement
leads
to
the
crystal-chemical
formula:PbMn2þ(Mn2þ,Fe2þ)2(V5þ,Ti,Fe3þ,&)18O38, which canbe generalised to XIIAVIBIVT2-yVIC18-xO38, allowing forthe flexibility needed to accommodate greater amounts ofV5þ. Assuming only pentavalent cations in C, and Mn2þ .
Fe2þ in T, the paseroite stoichiometric end–member would
thus be: PbMn2þMn2þV5þ14O38.
Since substantial Sr also exists within paseroite, it isconceivable that a new Sr- and V5þ-dominant member ofthe crichtonite group may also be found at Molinello. The
combination of Sr and V has been recently reported byBindi et al. (2011) in the new mineral bassoite,
SrV3O74H2O, also from the same Molinello fossil wood.

Acknowledgements: Editor Sandro Conticelli, Sergey
Krivovichev, Andrew Locock, Igor Pekov and two anonymous reviewers provided helpful comments on the manuscript. We are indebted to the collectors S. Bottoni, S.
Camarda and G. Sanguineti who found the fossil wood andto Giuseppe Finello who first attracted our attention to theblack prismatic crystals. Danilo Bersani is thanked for trying
to obtain a Raman spectrum on paseroite crystals. Part of thisstudy was funded by the John Jago Trelawney Endowment to
the Mineral Sciences Department of the Natural History
Museum of Los Angeles County.

Note: The mean quadratic elongation (l) and the angle variance (s2)were computed according to Robinson et al. (1971).

metal sites were observed, analogous to Grey & Lloyd’s
structure, and M6 was found to be unoccupied, therefore
requiring full occupancy of M2. In Armbruster & Kunz’s
U-rich senaite, extra metal sites M6–M9 were found,Fig. 2. A view of each of the polyhedral layers in paseroite, looking down c; from (a) where x ¼ 0, to (j) where x ¼ 1.
eschweizerbart_xxx

Paseroite, a new member of the crichtonite group1067

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Fig. 3. Arrangement of metal sites along the three-fold axis inpaseroite.

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Received 31 December 2011
Modified version received 14 April 2012
Accepted 21 May 2012eschweizerbart_xxx