Piccoliite, NaCaMn3+2(AsO4)2O(OH), a new arsenate from the manganese deposits of Montaldo di Mondovì and Valletta, Piedmont, Italy

Abstract Piccoliite, ideally NaCaMn3+2(AsO4)2O(OH), is a new mineral discovered in the Fe–Mn ore hosted in metaquartzites of the Montaldo di Mondovì mine, Corsaglia Valley, Cuneo Province, Piedmont, Italy. It occurs as small and rare black crystals and aggregates hosted by a matrix of quartz, associated with calcite and berzeliite/manganberzeliite. It has been also found in the Valletta mine near Canosio, Maira Valley, Cuneo Province, Piedmont, Italy, where it occurs embedded in quartz associated with grandaite, hematite, tilasite/adelite and rarely thorianite. The mineral is opaque (thin splinters may be very dark red), with brown streak and has a resinous to vitreous lustre. It is brittle with irregular fracture. No cleavage has been observed. The measured Mohs hardness is ~5–5.5. Piccoliite is non fluorescent. The calculated density is 4.08 g⋅cm–3. Chemical spot analyses by electron microprobe analysis using wavelength dispersive spectroscopy resulted in the empirical formula (based on 10 anions per formula unit) (Na0.64Ca0.35)Σ0.99(Ca0.75Na0.24)Σ0.99(Mn3+1.08Fe3+0.59Mg0.20Ca0.10)Σ1.97(As2.03V0.03Si0.01)Σ2.07O9(OH) and (Na0.53Ca0.47)Σ1.00(Ca0.76Na0.23Sr0.01)Σ1.00(Mn3+0.63Fe3+0.49Mg0.48Mn4+0.34Ca0.06)Σ2.00(As1.97P0.01Si0.01)Σ1.99O9(OH) for the Montaldo di Mondovì and Valletta samples, respectively. The mineral is orthorhombic, Pbcm, with single-crystal unit-cell parameters a = 8.8761(9), b = 7.5190(8), c = 11.689(1) Å and V = 780.1(1) Å3 (Montaldo di Mondovì sample) and a = 8.8889(2), b = 7.5269(1), c = 11.6795(2) Å, V = 781.43(2) Å3 (Valletta sample) with Z = 4. The seven strongest powder X-ray diffraction lines for the sample from Montaldo di Mondovì are [d Å (Irel; hkl)]: 4.85 (57; 102), 3.470 (59; 120, 113), 3.167 (100; 022), 2.742 (30; 310, 213), 2.683 (53; 311, 023), 2.580 (50; 222, 114) and 2.325 (19; 320, 214, 223). The crystal structure (R1 = 0.0250 for 1554 unique reflections for the Montaldo di Mondovì sample and 0.0260 for 3242 unique reflections for the Valletta sample) has MnO5(OH) octahedra forming edge-shared dimers; these dimers are connected through corner-sharing, forming two-up-two-down [[6]M2([4]TO4)4φ2] chains [M = Mn; T = As; φ = O(OH)] running along [001]. These chains are bonded in the a and b directions by sharing corners with AsO4 tetrahedra, giving rise to a framework of tetrahedra and octahedra hosting seven-coordinated Ca2+ and Na+ cations. The crystal structure of piccoliite is closely related to that of pilawite-(Y) as well as to carminite-group minerals that also show the same type of chains but with different linkage. The mineral is named after the mineral collectors Gian Paolo Piccoli and Gian Carlo Piccoli (father and son) (1926–1996 and b. 1953, respectively), the latter having discovered the type material at the Montaldo di Mondovì mine.

[1]  F. Cámara,et al.  As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: IV. Lombardoite, Ba2Mn3+(AsO4)2(OH) and aldomarinoite, Sr2Mn3+(AsO4)2(OH), description and crystal structure , 2022, Mineralogical Magazine.

[2]  F. Cámara,et al.  Armellinoite-(Ce), Ca4Ce4+(AsO4)4⋅H2O, a new mineral species isostructural with pottsite, (Pb3Bi)Bi(VO4)4⋅H2O , 2021, Mineralogical Magazine.

[3]  F. Cámara,et al.  Demagistrisite, the Missing Link in a Polysomatic Series from Lawsonite to Orientite , 2021 .

[4]  F. Hawthorne,et al.  Bond-length distributions for ions bonded to oxygen: results for the transition metals and quantification of the factors underlying bond-length variation in inorganic solids , 2020, IUCrJ.

[5]  S. Coelli,et al.  Characterization of ARDESIA: a 4-channel SDD X-ray spectrometer for synchrotron measurements at high count rates , 2019, Journal of Instrumentation.

[6]  P. Bonazzi,et al.  Manganiakasakaite-(La) and Ferriakasakaite-(Ce), Two New Epidote Supergroup Minerals from Piedmont, Italy , 2019, Minerals.

[7]  F. d’Acapito,et al.  The LISA beamline at ESRF. , 2019, Journal of synchrotron radiation.

[8]  F. Hawthorne,et al.  Bond-length distributions for ions bonded to oxygen: metalloids and post-transition metals , 2018, Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials.

[9]  R. Downs,et al.  Natropalermoite, Na2SrAl4(PO4)4(OH)4, a new mineral isostructural with palermoite, from the Palermo No. 1 mine, Groton, New Hampshire, USA , 2017, Mineralogical Magazine.

[10]  C. Carbone,et al.  Alpeite, Ca4Mn3+2Al2(Mn3+Mg)(SiO4)2(Si3O10)(V5+O4)(OH)6, a new ardennite-group mineral from Italy , 2017 .

[11]  L. Bindi,et al.  A multimethodic approach for the characterization of manganiceladonite, a new member of the celadonite family from Cerchiara mine, Eastern Liguria, Italy , 2017, Mineralogical Magazine.

[12]  P. M. Adams,et al.  Crimsonite, PbFe3+2(PO4)2(OH)2, the phosphate analogue of carminite from the Silver Coin mine, Valmy, Nevada, USA , 2016, Mineralogical Magazine.

[13]  A. Pieczka,et al.  Pilawite-(Y), Ca2(Y,Yb)2[Al4(SiO4)4O2(OH)2], a new mineral from the Piława Górna granitic pegmatite, southwestern Poland: mineralogical data, crystal structure and association , 2015, Mineralogical Magazine.

[14]  F. Hawthorne,et al.  Comprehensive derivation of bond-valence parameters for ion pairs involving oxygen , 2015, Acta crystallographica Section B, Structural science, crystal engineering and materials.

[15]  F. Cámara,et al.  As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: II. Braccoite, NaMn2+ 5 [Si5AsO17(OH)](OH), description and crystal structure , 2015, Mineralogical Magazine.

[16]  G. Sheldrick.  Crystal structure refinement with SHELXL , 2015, Acta crystallographica. Section C, Structural chemistry.

[17]  F. Cámara,et al.  Arsenic-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: I. Grandaite, Sr2Al(AsO4)2(OH), description and crystal structure , 2014, Mineralogical Magazine.

[18]  P. Orlandi,et al.  Lavoisierite, Mn2+8[Al10(Mn3+Mg)][Si11P]O44(OH)12, a new mineral from Piedmont, Italy: the link between “ardennite” and sursassite , 2013, Physics and Chemistry of Minerals.

[19]  M. Marcus,et al.  Determination of Mn valence states in mixed-valent manganates by XANES spectroscopy , 2012 .

[20]  M. Boiocchi,et al.  Coralloite, Mn2+Mn23+(AsO4)2(OH)2·4H2O, a new mixed valence Mn hydrate arsenate: Crystal structure and relationships with bermanite and whitmoreite mineral groups , 2012 .

[21]  Fujio Izumi,et al.  VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data , 2011 .

[22]  A. Fransolet,et al.  THE CRYSTAL STRUCTURE OF BERTOSSAITE, CaLi2[Al4(PO4)4(OH,F)4] , 2011 .

[23]  Uwe Kolitsch,et al.  Montaldo di Mondovì. Minerali della miniera di manganese e ferro , 2011 .

[24]  A. Fransolet,et al.  THE CRYSTAL STRUCTURE OF BERTOSSAITE , CaLi , 2011 .

[25]  Marcin Wojdyr,et al.  Fityk: a general-purpose peak fitting program , 2010 .

[26]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[27]  T. Armbruster,et al.  New Mn- and rare-earth-rich epidote-group minerals in metacherts : manganiandrosite-(Ce) and vanadoandrosite-(Ce) , 2006 .

[28]  M Newville,et al.  ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. , 2005, Journal of synchrotron radiation.

[29]  F. Farges.  Ab initio and experimental pre-edge investigations of the Mn K-edge XANES in oxide-type materials , 2005 .

[30]  P. Orlandi,et al.  Gramaccioliite-(Y), a new mineral of the crichtonite group from Stura Valley, Piedmont, Italy , 2004 .

[31]  R. Frost,et al.  Raman spectroscopy of some complex arsenate minerals-implications for soil remediation. , 2003, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[32]  F. Hawthorne,et al.  SEWARDITE, CaFe3+2(AsO4)2(OH)2, THE Ca-ANALOGUE OF CARMINITE, FROM TSUMEB, NAMIBIA: DESCRIPTION AND CRYSTAL STRUCTURE , 2002 .

[33]  B. Ravel,et al.  ATOMS: crystallography for the X-ray absorption spectroscopist. , 2001, Journal of synchrotron radiation.

[34]  Engen Libowitzky,et al.  Correlation of O-H stretching frequencies and O-H…O hydrogen bond lengths in minerals , 1999 .

[35]  R. Cabella,et al.  Occurrence of LREE- and Y-arsenates from a Fe-Mn deposit, Ligurian Brianconnais Domain, Maritime Alps, Italy , 1999 .

[36]  A. Ankudinov,et al.  REAL-SPACE MULTIPLE-SCATTERING CALCULATION AND INTERPRETATION OF X-RAY-ABSORPTION NEAR-EDGE STRUCTURE , 1998 .

[37]  Tim Holland,et al.  Unit cell refinement from powder diffraction data: the use of regression diagnostics , 1997, Mineralogical Magazine.

[38]  Max R. Taylor,et al.  The crystal structure of carminite: refinement and bond valence calculations , 1996, Mineralogical Magazine.

[39]  G. Nolze,et al.  POWDER CELL– a program for the representation and manipulation of crystal structures and calculation of the resulting X‐ray powder patterns , 1996 .

[40]  R. Cabella,et al.  Sr-rich hollandite and cryptomelane in braunite-ores of Maritime Alps and Eastern Liguria (Italy) , 1995 .

[41]  A. Palenzona,et al.  Mozartite, CaMn(OH)SiO 4 , a new mineral species from the Cerchiara Mine, northern Apennines, Italy , 1993 .

[42]  A. Wilson,et al.  International Tables for Crystallography. Volume C: Mathematical, Physical and Chemical Tables. Kluwer Academic Publishers, Dordrecht/Boston/London 1992 (published for the International Union of Crystallography), 883 Seiten, ISBN 0‐792‐3‐16‐38X , 1993 .

[43]  J. Grice,et al.  Attakolite; new data and crystal-structure determination , 1992 .

[44]  R. Cabella,et al.  Hollandite-cryptomelane and braunite in Mn-ores from upperJurassic meta-arenites and marbles (Internal Briançonnais, Maritime Alps) , 1992 .

[45]  A. Palenzona,et al.  Strontiopiemontite, a new member of the epidote group, from Val Graveglia, Liguria, Italy , 1990 .

[46]  G. Ivaldi,et al.  Bond valence vs bond length in O…O hydrogen bonds , 1988 .

[47]  R. Lefèvre.  Les nappes briançonnaises internes et ultrabriançonnaises dans les Alpes Cottiennes méridionales , 1982 .

[48]  P. Eisenberger,et al.  Extended x-ray absorption fine structure—its strengths and limitations as a structural tool , 1981 .

[49]  J. Mandarino,et al.  The Gladstone-Dale relationship; Part IV, The compatibility concept and its application , 1981 .

[50]  J. A. Mandarino.  The Gladstone-Dale relationship; Part III, Some general applications , 1979 .

[51]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[52]  P. Moore,et al.  Palermoite, SrLi2[Al4(OH)4(PO4)4]: its atomic arrangement and relationship to carminite,Pb2[Fe4(OH)4(AsO4)4 , 1975 .

[53]  W. H. Baur.  The geometry of polyhedral distortions. Predictive relationships for the phosphate group , 1974 .

[54]  W. Haidinger.  Mineralogische Beschreibung der Manganerze , 1828 .