Mineralogical Magazine, June 2014, Vol. 78(3), pp. 757–774

Arsenic-bearing new mineral species from Valletta mine,
Maira Valley, Piedmont, Italy: I. Grandaite,
Sr2Al(AsO4)2(OH), description and crystal structure
F. CÁMARA1,2,*, M. E. CIRIOTTI3, E. BITTARELLO1,2, F. NESTOLA4, F. MASSIMI5, F. RADICA6, E. COSTA1,
P. BENNA1,2 AND G. C. PICCOLI7
1

Dipartimento di Scienze della Terra, Università degli Studi di Torino, via Valperga Caluso 35, I-10125 Turin,
Italy
2
CrisDi, Interdepartmental Center for Crystallography, via Pietro Giuria 7, I-10125, Turin, Italy
3
Associazione Micromineralogica Italiana, via San Pietro 55, I-10073 Devesi-Cirié, Turin, Italy
4
Dipartimento di Geoscienze, Università degli Studi di Padova, via G. Gradenigo 6, I-35131 Padua, Italy
5
Dipartimento di Ingegneria Meccanica e Industriale, Università degli Studi Roma Tre, via della Vasca Navale 79,
I-00146 Rome, Italy
6
Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, largo San Leonardo Murialdo 1, I-00146
Rome, Italy
7
Amici del Museo ‘‘F. Eusebio’’, via Paruzza 1, I-12051 Alba, Italy[Received 19 January 2014; Accepted 27 February 2014; Associate Editor: A. Christy]
ABSTRACTThe new mineral species grandaite, ideally Sr2Al(AsO4)2(OH), has been discovered on the dump ofValletta mine, Maira Valley, Cuneo province, Piedmont, Italy. Its origin is related to the reaction
between the ore minerals and hydrothermal solutions. It occurs in thin masses of bright orange tosalmon to brown coloured crystals, or infrequently as fan-like aggregates of small (<1 mm) crystals,
with reddish-brown streak and waxy to vitreous lustre. Grandaite is associated with aegirine, baryte,
braunite, hematite, tilasite, quartz, unidentiﬁed Mn oxides and Mn silicates under study.
Grandaite is biaxial (+) with refractive indices a = 1.726(1), b = 1.731(1), g = 1.752(1). Its
calculated density is 4.378 g/cm3. Grandaite is monoclinic, space group P21/m, with a = 7.5764(5), b =5.9507(4), c = 8.8050(6) Å, b = 112.551(2)º, V = 366.62(4) Å3 and Z = 2. The eight strongest
diffraction lines of the observed X-ray powder diffraction pattern are [d in Å, (I), (hkl)]: 3.194(100)(2̄11), 2.981 (50.9)(020), 2.922 (40.2)(1̄03), 2.743 (31.4)(120), 2.705 (65.2)(112), 2.087 (51.8)(1̄23), 1.685 (24.5)(321), 1.663 (27.7)(132). Chemical analyses by electron microprobe gave (wt.%)
SrO 29.81, CaO 7.28, BaO 1.56, Al2O3 7.07, Fe2O3 2.34, Mn2O3 1.88, MgO 1.04, PbO 0.43, As2O5
44.95, V2O5 0.50, P2O5 0.09, sum 96.95; H2O 1.83 wt.% was calculated by stoichiometry from theresults of the crystal-structure analysis. Raman and infrared spectroscopies conﬁrmed the presence of(AsO4)3 and OH groups. The empirical formula calculated on the basis of 9 O a.p.f.u., in agreement
3+with the structural results, is (Sr 1.41 Ca 0.64 Ba 0.05 Pb 0.01 ) S=2.11 (Al 0.68 Fe 3+
0.14 Mn 0.12 Mg 0.13 ) S=1.07[(As0.96V0.01)S=0.97O4]2(OH), the simpliﬁed formula is (Sr,Ca)2(Al,Fe3+)(AsO4)2(OH) and the ideal
formula is Sr2Al(AsO4)2(OH).
The crystal structure was solved by direct methods and found to be topologically identical to that ofarsenbrackebuschite. The structure model was reﬁned on the basis of 1442 observed reﬂections to R1 =
2.78%. In the structure of grandaite, chains of edge-sharing M3+ octahedra run along [010] and sharevertices with T5+ tetrahedra, building up [M3+(T5+O4)2(OH, H2O)] units, which are connected through* E-mail: fernando.camaraartigas@unito.it
DOI: 10.1180/minmag.2014.078.3.21# 2014 The Mineralogical Society

F. CÁMARA ET AL.

interstitial divalent cations. Grandaite is named after the informal appellation of the province where thetype locality is located. The new mineral was approved by the International Mineralogical Association
Commission on New Minerals, Nomenclature and Classiﬁcation (IMA2013-059). The discovery of
grandaite and of other members of the group (description still in progress) opens up the possibility of
exploring the crystal chemistry of the brackebuschite supergroup.
K EY WORDS : grandaite, arsenate, arsenbrackebuschite group, new mineral species, crystal structure, Valletta,
Piedmont, Italy.

Introduction
ARSENIC is not a very abundant element. It
accounts for ~1.5 ppm of the Earth’s crust,making it the 47th most abundant element(Vaughan, 2006). On average, soils contain110 ppm of As, while seawater has only
1.6 ppb As (Emsley, 2011). In its most common
natural form, As occurs as colourless, odourless,crystalline As2O3 (the lethal ‘white arsenic’corresponding to both arsenolite and claudetite)
and As2O5, which are hygroscopic and readilysoluble in water forming acidic solutions. Arsenic
acid (containing As5+), AsO(OH)3, is a weak acid,
which forms arsenates responsible for As
contamination of groundwater, a problem that
affects many people (e.g. Mukherjee et al., 2006;
Twarakavi and Kaluarachchi, 2006), making thegeochemical investigation of As very important.
In some respects As compounds resemble thoseof P (another Group V element). The protonation
steps between the arsenate and As acid are similar
to those between phosphate and phosphoric acid.
The most common oxidation states for As are: 3
in the arsenides (such as alloy-like intermetallic
compounds), +3 in the arsenites and +5 in thearsenates and most organoarsenic compounds.
Arsenic also bonds to itself readily as seen for
example in the square As3
4 ions in the mineralskutterudite. In oxides, As+3 occurs typically as apyramidal AsO3 group in which all oxygens lie to
one side of the As+3 ion due to a stereoactive lonepair of electrons (Norman, 1998), while in the +5
oxidation state it is typically coordinated tetrahedrally.
To date >260 arsenates, <30 arsenites and <10silicoarsenates are recognized as valid mineral
species by the Commission on New Minerals,
Nomenclature and Classiﬁcation (CNMNC) of theInternational Mineralogical Association (IMA).
The recognition of new arsenate mineral species
at the Valletta mine dumps (Piedmont, Italy)
make this a signiﬁcant mineralogical locality.
Grandaite (IMA2013-059) represents the third
758

Sr-dominant arsenate of the mineral species
recognized as valid by IMA-CNMNC, after
arsenogoyazite, SrAl3(AsO4) (AsO3OH)(OH)6(Walenta and Dunn, 1984) and kemmlitzite,
SrAl3(AsO4)(SO4)(OH)6 (Hak et al., 1969). The
new mineral species strontiopharmacosiderite,
Sr0.5Fe3+
4 (AsO4)3(OH)4·4H2O (pers. comm. S. J.
Mills, 2013) was approved after grandaite(IMA2013-101).
This is the ﬁrst of a series of formal
descriptions of new As-bearing minerals fromthe Valletta mine. Samples containing grandaite
were collected by one of the authors (GCP) in
2001 and later in 2009 on the dumps of theValletta mine, Valletta Valley (‘Vallone della
Valletta’ in Italian), Canosio municipality, Maira
Valley, Cuneo province, Piedmont, Italy(44º23’42’’N, 7º5’42’’E, 2536 m asl). The
Valletta mine is a small Fe-Mn-As deposit thathas never been studied geologically or petrologically. The name of grandaite is for the informal
appellation of the Province where the type locality(Valletta mine) is located. The Cuneo Province ispopularly and historically called ‘‘la Granda’’ (theBig One) for its considerable extent, mostly in the
Alpine region (Maritime and Cottian Alps southof Mount Monviso). At 6903 km2 it is one of thebiggest in Italy.
A fragment of holotype material is deposited in
the mineralogical collection of the MuseoRegionale di Scienze Naturali di Torino,
Sezione di Mineralogia, Petrograﬁa e Geologia,
via Giovanni Giolitti 36, I10123 Torino, Italy,
catalogue number M/15999 and another in themineralogical collection of the Museo Civico
Archeologico e di Scienze Naturali ‘‘Federico
Eusebio’’, via Vittorio Emanuele 19, I12051
Alba, Cuneo, Italy, catalogue number G. 1723
prog. 505.
Not long after submitting the manuscript ourgood friend and colleague Bruno Lombardo
passed away. He very much loved the Alps andhas devoted much effort to the mineralogy ofPiedmont, contributing passionately to theNEW MINERAL SPECIES FROM PIEDMONT, ITALY

Antonio Bordello, alias Poncetto, of a small
assay of an iron mine in the territory of
Canosio, at the Valletta, with 12 fathoms of land
not so far, by the tithe of the ore.’’However, the deposit has never been studied
from a genetic point of view and available
geological data for the area studied are very
limited. Other than the historic text reported
above, there is no mention in the literature of theoccurrence of ore mineralization. Preliminary
work carried out during sampling of grandaite
showed that it is a small Fe-(Mn) deposit enrichedin As. Grandaite-bearing quartz veins are hosted
within compact, granular, dark red (verging on
black) quartzite. Blocks of this material have been
dug and piled up in a small landﬁll where they are
mixed with calcareous rocks, also from the
excavated material.
The new mineral is strictly associated withaegirine, adelite CaMg(AsO4)(OH), baryte, braunite, hematite, quartz, tilasite CaMg(AsO4)F,
unidentiﬁed Mn oxides and Mn silicates understudy.
In addition to grandaite, a number of other Asrich mineral species occur in this small dump,
some of them are currently under study. Theseﬁndings make the small dump of the Valletta
mine a reference locality for the study of arsenate
and silicoarsenate mineral species, similar to
those of the Graveglia Valley, Liguria, Italy(Antoﬁlli et al., 1983; Borgo and Palenzona,
1988; Palenzona, 1991, 1996). Other As-richminerals found in the rock samples collected in
the dump, although not strictly associated with
grandaite are: the arseniopleitecaryinite series(Ca,Na)NaMn 2+ (Mn 2+ ,Mg,Fe 2+ ) 2 (AsO 4 ) 3 (Na,Pb)(Ca,Na)CaMn2+
2 (AsO4)3, azurite, berzeliite NaCa 2 Mg 2 (AsO 4 ) 3 , manganberzeliite
N a C a 2 M n 22 + ( A s O 4 ) 3 , t i r a g a l l o i t e
5+
Mn2+
4 As Si 3O 12 (OH), braccoite (IMA 20135+
093) NaMn2+
5 [Si5As O17(OH)](OH); these arefound along with albite, calcite, diopside,ganophyllite, ilmenite, hollandite, malachite,magnesio-riebeckite, magnetite, Mn-bearing
muscovite, orthoclase, rutile, rhodonite andtitanite.

exploration and knowledge of many mineralogical localities. We dedicate this paper to his
memory.
Geological setting and mineral occurrence
The Valletta Fe-Mn deposit is located in the
Briançonnais Zone of the Cottian Alps.
Speciﬁcally, the Mn minerals are hosted in
Permian quartzites overlying quartzose conglomerates of the Verrucano facies and quartz-feldspar
ﬁne-grained schists derived from Permian rhyolitic volcanism of the so-called Axial Permian–
Carboniferous Zone (Franchi and Stella, 1930). A
major subvertical tectonic contact, Faille deCeillac (Gidon et al., 1994) separates the rocks
found at Valletta mine from the Middle Triassic
carbonate sequence of the Becco Grande to thenorth and from the Rocca La Meja ridge to thesouth. The rocks found at Valletta mine are part ofthe Bande de Marinet, the southernmost tectonic
zone of the Axial PermianCarboniferous Zone;
speciﬁcally it is part of Unit M3, the structurally
highest unit deﬁned in the Bande de Marinet by
Lefèvre (1982). During the Alpine tectonometamorphic cycle the rocks now exposed in theBande de Marinet were subjected to high-P,
low-T metamorphism of blueschist facies, theeffects of which are more evident in themetabasites intercalated in the metavolcanic
quartz-feldspar schists that often display thecharacteristic lawsonite-glaucophane assemblage(Franchi and Stella, 1930; Gidon et al., 1994).
Grandaite is probably the result of crystallizationfrom hydrothermal ﬂuids in an oxidizing environment (the occurrence of hematite, braunite andarsenates agree with this hypothesis); arsenic
could be derived from the surrounding Fe-Mn
ores, as observed by several authors in other smallhydrothermal Fe-Mn deposits from the Alps (e.g.
Brugger and Gieré, 1999).
A brief mineralogical note on the Valletta mine
was given by Piccoli (2002). During the ﬁrst
exploration, the remains of an old mining
operation, probably an open pit, were found at
the head of the Valletta Valley, near Canosio, in
the Maira Valley (Cuneo, Piedmont, Italy).
Historical information on a mine active in 1455
in the Saluzzo Marquisate (of which Canosio waspart) are summarized by Mangione (1999) and
Pipino (2010). The translation of the historicalmedieval text is as follows: ‘‘September 10, 1455:
Perpetual lease made by the Marquis Ludovico di
Saluzzo to Antonio Petro, late Petrino, andMineralogical characterization
Appearance and physical properties
Grandaite occurs as subhedral crystals in thinmasses, a few cm in size, with uneven fracture(Fig. 1), or infrequently as fan-like aggregates ofsmall crystals, in white veins of compact quartz

759

F. CÁMARA ET AL.

FIG. 1. Images of grandaite: (a) the holotype specimen deposited in the Museo Regionale di Scienze Naturali diTorino and (b) a fan-like aggregate (~1 cm61 cm) of grandaite in a quartz matrix, from the collection of G.C.
Piccoli. Photo G.C. Piccoli.

on reddish-brownish-black K-feldspar crossing, ina disorganized manner, the granular red-brownquartzite. Well-formed crystals, typically platy
tablets, are very rare and are rarely included in
more hyaline quartz and/or the blackish matrix on
fracture surfaces.
Individual crystals are bright orange to salmon
to brown and no twinning is observed. Grandaite istranslucent and has a reddish-brown streak, a waxy
to vitreous lustre and does not ﬂuoresce under SW
or LW ultraviolet light. Grandaite is opticallybiaxial (+), with 2V(meas.) = 52(2)º and 2V(calc.)= 53º. The measured refractive indices are a =1.726(1), b = 1.731(1), g = 1.752(1) (589 nm).
The mineral is brittle. No cleavage or parting isobserved. Hardness was measured by nanoindentation by using an Agilent Nano Indenter
G200 at the Università di Roma Tre – LIME
performed in CSM (continuous stiffness measurement) mode, with a frequency of 45 Hz,
amplitude of oscillation 2 nm, constant strain
rate of 0.05 s1 and a maximum penetration depthof 1000 nm. Results of hardness and modulus
proﬁles were obtained after averaging >25
different tests. The instrument was completely
re-calibrated before testing by performing a series
of indentations on a certiﬁed amorphous silica
reference sample. Observed elastic modulus is121.9  11 GPa (displacement 90110 nm) andhardness, H = 9.95  1.29 GPa (displacement90110 nm); Vickers Hardness was calculated
from H in order to determine Mohs hardness,
resulting in a Mohs hardness of 66. It is notpracticable to provide actual Vickers hardness
units because the method for obtaining hardness
used a continuous variation of the load. Density
was not measured due to the small crystal size andits intergrowths with adelite and baryte. The
calculated density obtained from the empiricalformula and unit-cell parameters measured during
the single-crystal study is 4.378 g/cm3.
Chemical data

760

The chemical composition of grandaite wasdetermined using a Cameca SX-50 electron
microprobe (wavelength-dispersive spectroscopy(WDS) mode) at the Dipartimento di Geoscienze(Università di Padova) on a thin section sampledfrom the holotype close to the place where thecrystal used for the diffraction study was extracted.
Major and minor elements were determined at
20 kV accelerating voltage and 20 nA beam
current (beam size = 2 mm), with 40 to 20 s
counting time on both peak and background. X-ray
counts were converted to oxide wt.% using the
PAP correction program supplied by Cameca(Pouchou and Pichoir, 1984, 1985).
The crystals studied in the thin section (Fig. 2)
were found to be homogeneous. On the basis ofpreliminary quantitative scanning electron microscopy (using energy-dispersive spectroscopy)
using a Cambridge S-360 microscope equippedwith an Oxford INCA Energy 200 (with ultrathin
window) at the Dipartimento di Scienze della
Terra (Università di Torino), analyses for Na, K,
Y, REE, F and Cl were not performed in thepresent WDS study; Si, Nb, Ti, Ta and S werechecked but were below detection limits. The
results of eight analyses are given in Table 1.
The empirical formula, calculated on the basisof 9 O a.p.f.u. (atoms per formula unit), is, withinrounding errors, (Sr1.41Ca0.64Ba0.05Pb0.01)S=2.11( A l 0 . 6 8 F e 30 .+1 4 M n 30 .+1 2 M g 0 . 1 3 ) S = 1 . 0 7

NEW MINERAL SPECIES FROM PIEDMONT, ITALY

Fe was considered as Fe3+ on the basis of sitebond length observed from structure reﬁnement.
The simpliﬁed formula is Sr2Al(AsO4)2(OH),
which requires SrO 41.68, Al2O3 10.23, As2O5
46.28, H2O 1.81, total 100.00 wt.%. The mean
refractive index n of grandaite, the calculated
density and the empirical formula yielded a
Gladstone-Dale compatibility index (Mandarino,
1979, 1981) of 0.032 rated as excellent.
Grandaite is unreactive and insoluble in 2 M
and 10% HCl and 65% HNO3.
Micro-Raman spectroscopy

FIG. 2. Image of the thin section of the holotype showing
grandaite in the marked area associated with a quartz
vein, cutting a braunite-hematite-bearing quartzite.
Plane-polarized light.

[(As0.96V0.01)S=0.97O4]2(OH). The presence of OH
was conﬁrmed by Raman and Fourier-transform
infrared spectroscopy (FTIR) (see next sections).

The Raman spectrum of grandaite (Fig. 3) was
obtained at the Dipartimento di Scienze della
Terra (Università di Torino) using a micro/macro
Jobin Yvon Mod. LabRam HRVIS, equipped witha motorized x–y stage and an Olympus microscope. The backscatter Raman signal wascollected with a 506 objective and the Raman
spectrum was obtained for a non-oriented crystal.
The 632.8 nm line of an He-Ne laser was used as
excitation; laser power was controlled by meansof a series of density ﬁlters. The minimum lateraland depth resolution were set to few mm. The
system was calibrated using the 520.6 cm1
Raman band of Si before each experimental
session. The spectra were collected with 26acquisitions and counting times ranging between
20 and 180 s. Spectral manipulation such asbaseline adjustment, smoothing and normalization

TABLE 1. Analytical data for grandaite.

SrO
CaO
BaO
Al2O3
Fe2O**
3
Mn2O3
MgO
PbO
As2O5
V2O5
P2O5
H2O*
Total

Wt.%

Range

Std. dev.

29.81
7.28
1.56
7.07
2.34
1.88
1.04
0.43
44.95
0.50
0.09
1.83
98.78

28.5130.57
6.797.74
0.792.63
6.767.79
2.092.63
1.362.14
0.761.40
0.160.55
44.4845.71
0.320.65
0.060.12
1.821.86
98.2399.18

0.64
0.48
0.56
0.38
0.28
0.24
0.18
0.13
0.46
0.12
0.02
0.01
0.30

Probe standard
celestine (La )wollastonite (Ka)baryte (La)
Al2O3 (Ka)
Fe2O3 (Ka)
MnTiO3 (Ka)
MgO (Ka)
Pb (Ma)GaAs (La)vanadinite (Ka)apatite (Ka)* Calculated by stoichiometry from the results of the crystal-structure analysis. **All Fe is considered as Fe3+ on thebasis of structure-reﬁnement results.
Std dev. = standard deviation

761

F. CÁMARA ET AL.

FIG. 3. Raman spectra of grandaite in the 2004000 cm1 region and between 200 and 1200 cm1.

were performed using the LabSpec 5 software
package (Horiba Jobin Yvon, 2004, 2005). Bandcomponent analysis was undertaken using the
Fityk software package (Wojdyr, 2010), whichenabled the type of ﬁtting function to be selected
and allows speciﬁc parameters to be ﬁxed orvaried accordingly. The spectrum was recorded
using the LabSpec 5 program from 100 to
4000 cm1 and the results of the spectroscopic
analysis are reported below.
Bands with frequencies between 200 and
600 cm1 correspond to As5+O bending vibrations, while bands lower than 200 cm 1correspond to lattice modes (120, 162, 213 cm1).
In detail, multiple Raman bands are observed at
308, 347, 382, 386, 418, 425 cm1. The ﬁrst twobands are assigned to the n2 (AsO4)3 symmetricbending vibration (E) and the latter four bands are
assigned to the n4 bending vibration (F2). The
assignment of these bands is in harmony with theanalysis of arsenate vibrations according toMyneni et al. (1998a,b) and Nakamoto (1986).
A broad band centred upon 500 cm1, which may
be resolved into component bands at 499, 512,
526 and 547 cm1 probably includes bands
attributable to the n4 (AsO4)3 bending mode.
The observation of multiple bands is characteristic of the reduced symmetry of the AsO4 unit in
the crystal (Frost and Keeffe, 2011). In the range
700950 cm1 the spectra are complex, showing
multiple bands that can be attributed to As5+O

stretching vibrations of AsO3
groups. A broad
4
envelope of overlapping bands centred on
858 cm1 can be resolved with band-component
analysis to show two intense bands at 857 and833 cm1. These bands are assigned to the n1(AsO4)3 symmetrical stretching and n3 (AsO4)3
antisymmetrical stretching modes. Other bands
are found at 899 and 790 cm1 which may also be
ascribed to the n3 (AsO4)3 antisymmetricalstretching mode or may be attributed to thehydroxyl deformation mode (Frost and Keeffe,2011). The absence of strong bands withfrequencies >950 cm1 indicates the absence of
H-, C-, N- and B-bearing groups in grandaite, but
in the region between 2500 and 4000 cm1
(hydroxyl stretching region) the spectrum displays
a considerable amount of noise and this is a resultof the low intensity of the bands. Due to this, thepresence of some measurable OH content could
not be excluded so the infrared spectrum of
grandaite was collected.
Infrared spectroscopy

762

Infrared (IR) spectra (Fig. 4) were collected at the
Università di Roma Tre using a Bruker Hyperion
3000 IR-microscope equipped with a liquid
nitrogen-cooled MCT detector. The powder
spectrum was collected with a Bruker Optics
VERTEX 70v FTIR spectrometer equipped with a
KBr beamsplitter, a DTGS detector and a

NEW MINERAL SPECIES FROM PIEDMONT, ITALY

FIG. 4. Infrared spectra: (left) single-crystal infrared spectrum; (right) powder spectrum collected with a MIRacle
Diamond ATR accessory.

crystal fragment showing sharp optical extinction
behaviour was used for collecting intensity data.
Crystal data and experimental details are reported
in Table 3. The intensities of 6095 reﬂections
with 12 < h < 12, 9 < k < 9 and 14 < l < 14were collected up to 69.9º2y using 0.2º frame andan integration time of 10 s. Data were integrated
and corrected for Lorentz and polarization background effects, using the package SAINT V6.45A(Bruker AXS, 2003). Data were corrected using
the empirical absorption correction (SADABS,
Sheldrick, 2008). Reﬁnement of the unit-cellparameters was based on 2404 measured reﬂections with I >10s(I). At room temperature, theunit-cell parameters are a = 7.5764(5), b =5.9507(4), c = 8.8050(6) Å, b = 112.551(2)º, V= 366.62(4) Å3, space group P21/m, Z = 2. The
a:b:c ratio is 1.273:1:1.480. A total of 1734
independent reﬂections were collected and thestructure was solved and reﬁned by means of the
SHELX set of programs (Sheldrick, 2008).

MIRacle Diamond ATR accessory. For both, thenominal resolution was 4 cm1 and 128 scans
were averaged for background and sample.
Infrared conﬁrmed the presence of H (absorption
band at ~3300 cm1) as hydroxyl showing strong
H bonding. Using the Libowitzky (1999) correlation a frequency of 3200 cm1 yields d(O···O) =2.70 Å and d(H···O) = 1.85 Å. The presence of anabsorption band at ~4100 cm1 in the m-IR
spectrum can be assigned to a combination ofstretching and bending modes of (OH) groups,
although they could be also assigned to
hypertones or combinations related to the(AsO4)3 group.
X-ray diffraction
The powder X-ray diffraction pattern of grandaite
was obtained at CrisDi (Università di Torino)using an Oxford Gemini R Ultra diffractometerequipped with a CCD area detector, with graphitemonochromatized MoKa radiation. Indexing of
reﬂections was based on a calculated powder
pattern obtained by the structural model, using thesoftware PLATON v140513 (Spek, 2009).
Experimental and calculated data are reported inTable 2.
The unit-cell parameters reﬁned from thepowder data with the software GSAS (Larson
and Von Dreele, 1994) are a = 7.575(1), b =5.9526(9), c = 8.765(2) Å, b = 112.55(2)º and V =366.62(4) Å3.
Single-crystal X-ray diffraction data werecollected using a Bruker AXS SMART APEX
diffractometer with a CCD detector (MoKa
radiation) at Università di Pavia (Pavia, Italy). A

Description of the structure
Structure model
The structure was reﬁned starting from the atom
coordinates of arsenbrackebuschite (Hofmeister
and Tillmanns, 1978). Site-scattering values werereﬁned for the cation sites using two scattering
curves contributing proportionally and with a sum
constrained to full occupancy: As and V wereused for the sites T(1) and T(2); Al and Fe wereconsidered for the M site; Sr and Ca were used for
the A(1) site; and Sr and Ba for the A(2) site. A
peak of ~2.7 e.Å3 was found in the differenceFourier map, close to the A(2) site (~0.7 Å) and it763

F. CÁMARA ET AL.

TABLE 2. X-ray powder diffraction data for grandaite.
The eight strongest reﬂections are reported inbold*.
h

k

l

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

0
0
1
0
1
1
2
0
1
0
2
2
1
1
2
1
2
1
0
0
2
1
2
1
0
1
2
0
1
0
3
3
1
0
2
3
2

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

dobs (Å)

3.194
2.981
2.922
2.798
2.743
2.705
2.563
2.486
2.455
2.400
2.315
2.144
2.127
2.108
2.087
2.047

dcalc (Å)
8.131
4.066
3.597
3.499
3.357
3.193
2.975
2.935
2.930
2.842
2.794
2.710
2.565
2.485
2.461
2.332
2.153
2.089

Irel

100.00
50.93
40.20
6.55
31.39
65.19
5.02
21.13
16.05
7.45
12.81
8.04
11.19
5.38
51.75
7.05

2.044
2.017
1.999
1.891
1.845

1.892
1.850
1.822

1.759

Icalc
10.9
9.3
11.7
12.5
6.3
100.0
83.0
80.4
11.6
14.2
8.2

Site occupancies

61.0
9.7
10.8
9.3
7.2
11.9
29.5
18.0

5.55
5.56
10.70
22.42

22.8
16.5
8.9

10.32
1.757

1.745
1.685
1.663
1.597

Reﬁnement converged to R1 = 0.029 for 1442
observed reﬂections with Fo >4s(Fo) and 84
parameters. Tables 4, 5 and 6 report: atom
coordinates; displacement parameters; andselected bond distances and angles, respectively.
Bond-valence calculations using the parametersof Brown (1981) are reported in Table 7. Tablesof structure factors and a crystallographic
information ﬁle (CIF) have been deposited with
the Principal Editor of Mineralogical Magazine
and are available from www.minersoc.org/pages/
e_ journals/dep_mat_mm.html.

13.1
5.93

1.749
1.685
1.662
1.596

24.52
27.65
14.40

6.0
19.9
13.1
9.8

* Only reﬂections with Irel >5s(Irel) are listed.

was considered occupied by Pb. Due to the low
occupancy (i.e. 0.03 a.p.f.u. of Pb) it was not
added to the model. Another peak in the
difference-Fourier map was found close to O(7)and added to the model as an H atom with ﬁxed
coordinates, an isotropic displacement factor of
0.02 Å2 and full occupancy. Scattering curves forneutral atoms were taken from the International
Tables for Crystallography (Wilson, 1992).
764

Cation sites
The observed site scattering 15.40(3) e.p.s.
(electrons per site) at the M site agrees well withthe chemical data conﬁrming an Al dominance atthat site (Al0.68 + Mg0.13 = 0.81 from chemical
analysis, to be compared with 0.82 Al a.p.f.u.,
from the reﬁnement), with a minor contribution of3+
heavier scatterers (Fe3+
0.14Mn0.12 = 0.26 a.p.f.u. vs.
0.18 Fe a.p.f.u. from the reﬁnement, Table 4). The
observed average bond length at M sites (1.962 Å,Table 6) is too short for Fe2+ and Mn2+. In
addition, incident bond valence at the M site is inagreement with average charge being dominantly
3+, i.e. considering both Fe3+ and Mn3+ at the Msites. The trivalent oxidation state of Fe and Mn
agrees with the oxidized nature of the ore.
Therefore, both elements were considered to be
in a trivalent oxidation state for formulacalculation (see chemistry above). Site distribution at the A sites was obtained according to thestructure reﬁnement that shows a clear differencein scattering in both sites: 29.9(1) electrons persite at the A(1) site and 39.4(2) electrons per siteat the A(2) site. Therefore, Sr0.55Ca0.45 is assignedto A(1) and Sr0.92Ba0.08 to A(2). Bond-valencecalculations indicate that both the A(1) and A(2)sites are compatible with the dominance ofdivalent cations at these sites. Site-scatteringvalues obtained for T sites are equal, although
average bond lengths and distortion parameters
were signiﬁcantly different (Table 6). The limited
quantity of V observed in WDS analyses and theabsence of high-charge cations that may potentially enter the T sites (P, S, Si) lead to V being
considered disordered equally among both sites.
The distortion is therefore interpreted as an
intrinsic feature of the structure. The cation
3+ 2+
sums at T sites implies T5+
which
4 M2 A4+
accounts for 34 .

NEW MINERAL SPECIES FROM PIEDMONT, ITALYTABLE 3. Crystal data and summary of parameters describing the data collection and reﬁnement for grandaite.
Crystal system
Space group
Unit-cell dimensionsa (Å)b (Å)c (Å)b (º)
V (Å3)Z
m (mm1)
F(000)
Dcalc (g cm3)
Crystal size (mm)Radiation type
Temperature (K)y range for data collection (º)
Rint
Reflections collected
Independent reflections
Fo>4s(F)
Refinement method
No. of refined parameters
Final Robs
R1
wR2 Fo>4s(F)Highest peak/deepest hole (e Å3)
Goodness of fit on F2

Monoclinic
P21/m
7.5764(5)5.9507(4)8.8050(6)112.551(2)366.62(4)
2
20.34
443
4.378
0.13060.08560.080
MoKa (0.71073 Å)
298
2.535.0
0.026
6095
1734
1442
least-squares matrix: full
84
0.037
0.029
0.065
+2.57 / 0.76
1.074

TABLE 4. Multiplicities, fractional atom coordinates and equivalent isotropic displacement parameters (Å2) for
grandaite*.
Site

Mult.

T(1)

2e

T(2)

2e

M

2a

A(1)

2e

A(2)

2e

O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
H(7)

4f
2e
2e
4f
2e
2e
2e
2e

Occ.
0.886(9)As0.114(9)V
0.884(9)As0.116(9)V
0.815(5)Al
0.185(5)Fe
0.548(5)Sr
0.452(5)Ca
0.921(7)Sr
0.079(7)Ba

1.000

x/a

y/b

z/c

Uiso

0.43733(5)

0.17111(4)0.0124(1)0.03113(4)

0.33393(4)0.0103(1)0000.0106(2)0.25931(6)

0.73723(5)0.0188(1)0.67546(4)

0.58860(4)0.0133(1)0.0231(3)0.2635(4)0.9109(4)0.5055(2)0.5209(5)0.1923(3)0.8303(3)0.70430.5144(3)
0.0223(3)

0.7853(2)0.4501(3)0.4550(4)0.2905(2)0.0207(4)0.0638(3)0.9207(3)0.92300.0203(4)0.0265(6)0.0320(7)0.0197(4)0.0391(8)0.0210(5)0.0137(5)0.0200* The temperature factor has the form exp(T) where T = 8p2U(sin(y)/l)2 for isotropic atoms.

765

F. CÁMARA ET AL.

TABLE 5. Anisotropic displacement parameters (Å2) for grandaite*.
Site

U11

U22

U33

U23

U13

U12

T(1)
T(2)
M
A(1)
A(2)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)

0.0124(2)0.0124(2)0.0139(4)0.0179(2)0.0147(2)0.0330(1)0.0152(12)0.0334(15)0.0226(8)0.041(2)0.0149(11)0.0121(10)0.0114(2)0.0105(2)0.0087(4)0.0206(2)0.01477(14)0.0132(7)0.040(2)0.041(2)0.0153(8)0.059(2)0.0216(12)0.0150(11)0.0114(2)0.0093(2)0.0090(4)0.0226(2)0.01246(15)0.0156(8)0.0217(13)0.035(2)0.0177(8)0.028(2)0.0207(12)0.0124(10)000.0000(2)000.0020(6)000.0026(6)0000.00242(12)0.00556(12)0.0039(3)0.0131(2)0.00758(10)0.0105(7)0.0041(10)0.0273(14)0.0039(7)0.0249(14)0.0005(9)0.0029(8)000.0004(2)000.0025(6)000.0017(6)000* The temperature factor has the form exp(T) where T = 2p2Sij(h(i)h(j)U(i,j)a*(i)a*(j).

Anion sites
There are seven anion positions in the structureof grandaite, two of them on general positions,accounting for a total of 18 anions per unit cell.
The bond-valence table (Table 7) shows that oneof seven anion sites shows a bond-valence

incidence close to 2 vu (valence units), while
the O(7) site has a lower contribution (1.272 vu)compatible with a monovalent anion at this site.
The absence of F in the chemical analyses(Table 2) indicates that this site must therefore
host a hydroxyl group. In fact, a maximum was

TABLE 6. Selected interatomic distances (Å) and angles (o) for grandaite*.
T(1) O(4) (62)
O(5)
O(6)
<T(1)O>
V (Å3)s2 *l*

1.671(2)1.673(3)1.730(2)
1.686
2.449
12.93
1.0034

T(2) O(3)O(2)O(1) (62)<T(2)O>
V (Å3)s2 *l*

1.647(3)1.663(3)1.704(2)
1.680
2.430
0.49
1.0006

O(7) (62)O(1) (62)O(6) (62)<M O>
V (Å3)s2 *l*

1.914(1)1.966(2)2.006(2)
1.962
9.934
32.00
1.0097

M

A(1) O(4)( 62)O(5)O(1) (62)
O(2)
O(3)
O(6)
<A(1)O>
V (Å3)2.489(2)2.523(3)2.537(2)2.541(3)2.848(3)3.105(3)
2.634
26.80

A(2)O(3)O(4) (62)O(7)O(4) (62)O(2)O(1) (62)O2 (62)<A(2)O>
V (Å3)2.485(3)2.600(2)2.701(3)2.791(2)2.883(3)2.986(2)3.050(1)
2.811
49.28

O(7) –H(7)O(7) _O(5)O(5) _H(7)

0.96
2.80
1.89

* Mean quadratic elongation (l) and the angle variance (s2) were calculated according to Robinson et al. (1971).

766

NEW MINERAL SPECIES FROM PIEDMONT, ITALYTABLE 7. Bond-valence calculations for grandaite.
Site

T(1)

T(2)

M

A(2)

0.2762;0.1062;0.13
0.0962;62?
0.37
0.2762;0.1762;O(1)1.1762;

O(2)

1.30

0.27

1.35

0.11

O(3)
O(4)

1.27

O(5)
O(6)
O(7)

1.27
1.10

b.v.
Agg. ch.

4.91
5.00

0.4662;

A(1)

62;

0.30
0.28
0.07

0.4262;62?
0.5362;62?
4.99
5.00

62;

2.82
2.88

1.87
2.00

H(7)

S
2.00
1.88
1.83
2.01

0.18
0.21

0.81

1.73
2.01
2.08

1.97
1.98

0.99
1.00

17.55
17.86

b.v. = bond valence; Agg. ch. = aggregate charge.

minor Ba orders in the larger 11-coordinated A(2)site (<A(2)O> = 2.811 Å) in grandaite. In
arsenbrackebuschite Pb occupies both sites but isshifted off-centre as is usual for its lone-pair
conﬁguration. The small quantity of Pb found in
grandaite at the A(2’) site also follows thisconﬁguration. This Pb off-centre displacement
has been reported previously e.g.: synthetic
Pb2(Pb,K)4[Si8O20]O (Moore et al., 1985); Pb
replacing Ba in hyalotekite (Moore et al., 1982;
Christy et al., 1998); or Pb replacing REE inlusernaite-(Y) (Biagioni et al., 2013). The
distortion observed for the T(2) site, along withthe low bond-valence incidence at O(5) represents
a stressed environment for this structure.

found at ~0.96 Å in the Fourier difference andadded to the model as atom H(7). The H at H(7) is
at 1.895 Å from the O(5) atom which has a bondvalence sum of 1.55 vu and so is likely to receivea H bond. Therefore, there is a H bond with O at
O(5) ensuring a further contribution of bondvalence to this site (Table 7). The structuralmodel thus conﬁrms OH···O = 2.8 Å, in good
agreement with IR data. The anion part of thestructure is O16(OH)2, which accounts for 34.
Structure topology
The crystal structure of grandaite (Figs 56) is
topologically identical to that of arsenbrackebuschite. Chains of [M3+,2+(T5+O4)2(OH, H2O)]
units are connected through interstitial divalentcations. The M3+ octahedron shares edges withother octahedra forming a chain along [010]. The
shared edge has one anion that can be an OH
group or a H2O molecule, depending on the
charge of the cation at the octahedron and theother anion is shared with the apex of a T5+O4
tetrahedron (the T(1) site). The remaining four
anions coordinating the octahedron are linked tothe edge of another T5+O4 tetrahedron (the T(2)site) alternating in both sides (Fig. 6). Minor V isdisordered among the two arsenate tetrahedra.
Decorated chains of octahedra link together
through bonding with two symmetrically independent interstitial cations at the A(1) and A(2)sites and H bonding (O_O = 2.8 Å). Minor Ca
orders preferentially in the smaller eight-coordinated A(1) site (<A(1)O> = 2.634 Å), while

Related minerals

767

Grandaite, Sr2Al(AsO4)2(OH), is the As-dominantanalogue of goedkenite, Sr2Al(PO4)2(OH) and the
Sr-As -dominant analogue of bearthite,
Ca2Al(PO4)2(OH). It is the ﬁrst Al member of
the arsenbrackebuschite group in the brackebuschite supergroup (Table 8). The brackebuschite supergroup has the general formulaviii,xi 2+,1+ vi
A2
M 3 + , 2 + H 0 1 [ i v ( T 5 + , 6 + ) O 4 ] 2[Oy,(OH)1y]. Subgroups are divided on the basisof the charge species dominance at the T sites. The
crystal chemistry of this supergroup is under study
as part of a broader project. A comparison of theproperties of the members of the arsenbrackebuschite group is reported in Table 9. In theStrunz System (Strunz and Nickel, 2001) grandaiteﬁts in subdivision 8.B.G, phosphates, etc. with

F. CÁMARA ET AL.

FIG. 5. Projection of the grandaite structure down [010]; the unit cell is indicated by thick red lines. Ellipsoids at 90%
probability. Atom sites labelled in the ﬁgure are: T(1): light green, T(2): dark green, M: light blue, A(1): lilac, A(2):violet, H(7): grey, oxygen sites: red. Drawing obtained with VESTA 3 (Momma and Izumi, 2011).

additional anions, without H2O, with mediumsized and large cations, (OH, etc.).
Isotypic structures occur in the synthetic
compounds Na 2 Cr 3+ (Cr 6+ O 4 ) 2 (OH), K 2 Cr 3+(Cr6+O4)2(OH) (Jonsson, 1970) andPb3(P1.15V0.85)2O8 (Kiat et al., 1993). The
minerals fornacite, Pb2Cu2+[(CrO4)(AsO4)](OH)(Lacroix, 1915, 1916; Cocco et al., 1967; Fanfani

FIG. 6. Detail of the chain of M octahedra. Ellipsoids at 50% probability. Atom sites labelled in the ﬁgure; colours as
in Fig. 5. Drawing obtained with VESTA 3 (Momma and Izumi, 2011).

768

769

Goedkenite (23)
Sr2Al(PO4)2(OH)

Bearthite (17,18,19)
Ca2Al(PO4)2(OH)

Tsumebite (9,24,25,26,27,28,29)
Pb2Cu[(PO4)(SO4)](OH)Bushmakinite (20,21,22)
Pb2Al[(PO4)(VO4)](OH)

Arsentsumebite (3,4,5,29)
Pb2Cu[(AsO4)(SO4)](OH)(7)

Refs: (1) Abraham et al. (1978); (2) Hofmeister and Tillmanns (1978); (3) Vésignié (1935); (4) Bideaux et al. (1966); (5) Zubkova et al. (2002); (6) Clark et al. (1997);
Rammelsberg (1880); (8) Donaldson and Barnes (1955); (9) Fanfani and Zanazzi (1967); (10) Foley et al. (1997); (11) González del Tánago et al. (2003);(12)
de Villiers (1943); (13) Harlow et al. (1984); (14) Basso et al. (1987); (15) Williams (1973); (16) Matsubara et al. (2004); (17) Chopin et al. (1993); (18) Brunet andChopin (1995); (19) Roth (2007); (20) Pekov et al. (2002); (21) Yakubovich et al. (2002); (22) Pekov (2007); (23) Moore et al. (1975); (24) Rosický (1912);(25)
Busz (1912); (26) Spencer (1913); (27) LaForge (1938); (28) Nichols (1966); (29) Schlüter et al. (1994); (30) this study. *Needs further study.

Tokyoite (16)Ba2Mn3+(VO4)2(OH)

Heyite* (15)
Pb5Fe2+2 (VO4)2O4

Gamagarite (12,13,14)
Ba2Fe3+(VO4)2(OH,H2O)

Calderónite* (11)
Pb2Fe3+(VO4)2(OH)Feinglosite (6)Pb2Zn(AsO4)2(OH,H2O)

Grandaite (30)
Sr2Al(AsO4)2(OH)

Brackebuschite (7,8,9,10)
Pb2Mn3+(VO4)2(OH)

Arsenbrackebuschite (1,2)
Pb2Fe3+(AsO4)2(OH,H2O)

2+iv 5+ 6+—————————— Brackebuschite supergroup, A(1)2+ A(2)2+ vi[M3+x ,M1x] [ (Tz ,T1z)O4]2 (O1yOHy) ——————————
Arsenbrackebuschite group
Brackebuschite group
Goedkenite group
Tsumebite group
As dominant at T
V dominant at T
P dominant at T
P or As + S or V dominant at T

TABLE 8. Minerals of the brackebuschite supergroup. References are given in brackets.

NEW MINERAL SPECIES FROM PIEDMONT, ITALYF. CÁMARA ET AL.

and Zanazzi, 1968) and vauquelinite,
Pb2Cu2+[(CrO4)(PO4)](OH) (Berzelius, 1818;
Fanfani and Zanazzi, 1968), the members of thetörnebohmite group [törnebohmite-(Ce),Ce 2 Al(SiO 4 ) 2 (OH) and törnebohmite-(La),
La2Al(SiO4)2(OH) (Geijer, 1921; Wherry, 1921;
Shen and Moore, 1982)], molybdofornacite,
Pb2Cu2+[(MoO4)(AsO4)](OH) (Medenbach etal., 1983) and the potential, but never approved,

P-analogue of molybdofornacite,
Pb 2 Cu 2 + [(MoO 4 )(PO 4 )](OH), (Nickel and
Hitchen, 1994) present derivative structure
analogues characterized by doubling of one unitcell parameter or a shift in the origin (anddifferent symmetry). These structures are topologically identical to brackebuschite supergroupstructures, the doubling of the cell being due toordering of anions in the structure of fornacite and

TABLE 9. Comparison of minerals of the arsenbrackebuschite group.
Arsenbrackebuschite
Reference
FormulaSystemSpace groupa (Å)bcb (º)
V (Å3)Z
a:b:c
Dmeas (g cm3)
Dcalc (g cm3)
Strongest lines in
the powder pattern: dobs (Å)(I)Feinglosite*

(1,2)
(3)
Pb2Fe3+(AsO4)2(OH,H2O)
Pb2Zn(AsO4)2·H2O
Monoclinic
Monoclinic
P21/m
P21, P21/m
7.764(2)7.766(6)6.045(2)5.955(3)9.022(2)8.973(6)112.5
112.20(6)391.2
384.2(4)221.2843:1:1.4924
1.5068: 1:1.3041
n.d.
n.d.
6.54
6.52
3.012 (100), 3.268 (90), 2.777 3.246(100), 2.988(60), 2.769(60), 2.313 (30), 2.133 (30), (60), 4.85(50), 2.107(50),3.659 (30), 2.293 (30)
4.92 (25), 3.68 (25)

Optical (sign)
a
b
g
2V(º)
Colourbiaxial ()
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
honey-yellow, yellow, brown, pale olive-green
green
Pleochroism
honey-yellow to bright yellow non pleochroic
Hardness (Mohs) 45
45
Streakpale brownish
white
Lustreresinous to adamantine
adamantine
FluorescentTenacity
sectileCleavageperfect on {010}Twinning
complex, observedHabit and forms tiny flat plates and laths
multiple individuals, inradiating botryoidal
aggregates subhedral grains
Association
beudantite, anglesite, mime- goethite, anglesite, wulfenite,
tite, bayldonite, stolzite
chalcocite, arsendescloizite,
gypsumGrandaite
This work
Sr2Al(AsO4)2(OH)
Monoclinic
P21/m
7.5764(5)5.9507(4)8.8050(5)112.551(1)366.62(4)2
1.273:1:1.480
n.d.
4.38
3.194 (100), 2.705 (65),2.087 (52), 2.981 (51),2.922 (40), 2.743 (31),1.663 (28), 1.685 (25)biaxial (+)
1.726(1)1.731(1)1.752(1)52(2) (meas), 53 (calc)orange to salmon to brown
non-pleochroic
66.5
reddish brown
vitreous
non-fluorescentbrittlenot observed
none observed

aegirine, adelite, baryte,
braunite, hematite, quartz,
tilasite, unidentified Mnoxides and Mn silicates

Refs: (1)Abraham et al. (1978); (2)Hofmeister and Tillmanns (1978); (3)Clark et al. (1997).
* unit-cell parameters transformed to compare the structure relationships between group phases.

770

NEW MINERAL SPECIES FROM PIEDMONT, ITALY

the shift of the origin and different symmetry
elements due to order of Cu at the M sites invauquelinite, probably due to Jahn-Teller effects.
The latter are also structurally related to themembers of descloizite, fairﬁeldite, roselite andtsumcorite groups.
Acknowledgements
The authors thank Bruno Lombardo (CNR-IGGTorino) for his assessment support in ﬁeld work at
the Valletta and Fabio Bellatreccia (Università diRoma Tre) for providing IR data. FC acknowledges Chiara Domeneghetti (Università di Pavia)
for access to the Bruker AXS diffractometer
under a collaboration agreement between the
Dipartimento di Scienze della Terra (Università
di Torino) and the Dipartimento di Scienze della
Terra e Ambiente (Università di Pavia). Carmelo
Sibio (Università di Torino) is thanked for thinsection preparation. Raul Carampin (CNR-IGGPadova, Italy) is thanked for support with the
WDS analysis. Cristian Biagioni, Mark Welchand Pete Leverett are thanked for their constructive reviews. FC, PB and EC acknowledge thesupport of the project ‘‘PROactive Managementof GEOlogical Heritage in the PIEMONTE
Region’’ (www.progeopiemonte.it/en) cofounded by the University of Turin Compagnia di San Paolo Bank Foundation‘‘JCAPC - Progetti di Ateneo 2011’’ grant online B1 ‘‘Experimental Sciences and Technology’’(Project Id: ORTO11Y7HR, P.I. Prof. Marco
Giardino). FC and EB thank the MIUR and the
AMI for the co-funding of a research contract for
EB for the year 2013.
References
Abraham, K., Kautz, K., Tillmanns, E. and Walenta, K.
(1978) Arsenbrackebuschite, Pb2(Fe,Zn)(OH,H2O)[AsO4]2, a new arsenate mineral. Neues Jahrbuch
für Mineralogie, Monatshefte, 1978, 193196.
Antoﬁlli, M., Borgo, E. and Palenzona, A. (1983) I
nostri minerali. Geologia e mineralogia in Liguria.
SAGEP Editrice, Genoa, Italy, 296 pp. [in Italian].
Basso, R., Palenzona, A. and Zeﬁro, L. (1987)
Gamagarite: new occurrence and crystal structure
reﬁnement. Neues Jahrbuch für Mineralogie,
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