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Penberthycroftite, [Al6(AsO4)3(OH)9(H2O)5]·8H2O, a second new hydrated aluminium arsenate mineral from the Penberthy Croft mine, St. Hilary, Cornwall, UK

Published online by Cambridge University Press:  02 January 2018

I. E. Grey ,
J. Betterton ,
A. R. Kampf ,
C. M. Macrae ,
F. L. Shanks  and
J. R. Price
I. E. Grey*
Affiliation:
CSIRO Mineral Resources, Private bag 10, Clayton South, Victoria 3169, Australia
J. Betterton
Affiliation:
Haslemere Educational Museum, 78 High Street, Haslemere, Surrey GU27 2LA, UK
A. R. Kampf
Affiliation:
Mineral Sciences Dept., Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
C. M. Macrae
Affiliation:
CSIRO Mineral Resources, Private bag 10, Clayton South, Victoria 3169, Australia
F. L. Shanks
Affiliation:
School of Chemistry, Monash University, Clayton, Victoria 3800, Australia
J. R. Price
Affiliation:
Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia
*
*E-mail: Ian.Grey@csiro.au
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Abstract

Penberthycroftite, ideally [Al6(AsO4)3(OH)9(H2O)5]·8H2O, is a new secondary aluminium arsenate mineral from the Penberthy Croft mine, St. Hilary, Cornwall, England, UK. It occurs as tufts of white, ultrathin (sub-micrometre) rectangular laths, with lateral dimensions generally < 20 μm. The laths are flattened on {010} and elongated on [100]. The mineral is associated with arsenopyrite, bettertonite, bulachite, cassiterite, chalcopyrite, chamosite, goethite, liskeardite, pharmacoalumite–pharmacosiderite and quartz. Penberthycroftite is translucent with a white streak and a vitreous to pearly lustre. The calculated density is 2.18 g/cm3. Optically, only the lower and upper refractive indices could be measured, 1.520(1) and 1.532(1) respectively. No pleochroism was observed. Electron microprobe analyses (average of 14) with H2O obtained from thermogravimetric analysis and analyses normalized to 100% gave Al2O3 = 31.3, Fe2O3 = 0.35, As2O5 = 34.1, SO3 = 2.15 and H2O = 32.1. The empirical formula, based on nine metal atoms and 26 framework anions is [Al5.96Fe0.04(As0.97Al0.03O4)3(SO4)0.26(OH)8.30(H2O)5.44](H2O)7.8, corresponding to the ideal formula [Al6(AsO4)3(OH)9(H2O)5]·8H2O. Penberthycroftite is monoclinic, space group P21/c with unit-cell dimensions (100 K): a = 7.753(2) Å, b = 24.679(5) Å, c = 15.679(3) Å and β = 94.19(3)°. The strongest lines in the powder X-ray diffraction pattern are [dobs in Å(I) (hkl)] 13.264(46) (011); 12.402(16)(020); 9.732(100)(021); 7.420(28)(110); 5.670(8)(130); 5.423(6)(1̄31). The structure of penberthycroftite was solved using synchrotron single-crystal diffraction data and refined to wRobs = 0.059 for 1639 observed (I> 3σ(I)) reflections. Penberthycroftite has a heteropolyhedral layer structure, with the layers parallel to {010}. The layers are strongly undulating and their stacking produces large channels along [100] that are filled with water molecules. The layers are identical to those in bettertonite, but they are displaced relative to one another along [001] and [010] such that the interlayer volume is decreased markedly (by ∼10%)relative to that in bettertonite, with a corresponding reduction in the interlayer water content from 11 H2O per formula unit (pfu) in bettertonite to 8 H2O pfu in penberthycroftite.

Type
Research Article
Information
Mineralogical Magazine , Volume 80 , Issue 7 , December 2016 , pp. 1149 - 1160
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2016

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References

Betterton, J. (2000) Famous mineral localities: Penberthy Croft mine, St. Hilary, Cornwall, England. UK Journal of Mines and Minerals, 20, 7—37.Google Scholar
Bevins, R.E., Young, B., Mason, J.S., Manning, D.A.C. and Symes, R.F. (2010). Mineralization of England and Wales. Geological Conservation Review Series, No 36. Joint Nature Conservation Committee, Peterborough, UK, pp. 496–99.Google Scholar
Bowell, R.J., Alpers, C.N., Jamieson, H.E., Nordstrom, D.K. and Majzlan, J. (editors) (2014) Arsenic: Environmental Geochemistry, Mineralogy, and Microbiology.Reviews in Mineralogy and Geochemistry, 79. Mineralogical Society of America and the Geochemical Society, Chantilly, Virginia, USA, 635 pp.Google Scholar
Cooper, M.A., Abdu, Y.A., Ball, N.A., Hawthorne, F.C., Back, M.E., Tait, K.T., Schlüter, J., Malcherek, T., Pohl, D. and Gebhard, G. (2012). Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, a new arsenate mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia: description and crystal structure. Mineralogical Magazine, 76, 1119–1131.CrossRefGoogle Scholar
Farrugia, L.J. (2012) WinGX and ORTEP for Windows: an update. Journal of Applied Crystallography, 45, 849–854.CrossRefGoogle Scholar
Frost, R.L., Scholz, R. and Lopez, A. (2015) Raman and spectroscopic characterization of the arsenate-bearing mineral tangdanite and in comparison with the discredited mineral clinotyrolite. Journal of Raman Spectroscopy, 46, 920–926.CrossRefGoogle Scholar
Gao, Q., Li, F., Wang, Y., Xu, L., Bai, J. and Wang, Y. (2014) Organic functionalization of polyoxometalate in aqueous solution: self-assembly of a new building block of ﹛VMo6O25﹜ with triethanolamine. Dalton Transactions, 43, 941–944.CrossRefGoogle ScholarPubMed
Grey, I.E., Mumme, W.G., MacRae, C.M., Caradoc-Davies, T., Price, J.R., Rumsey, M.S. and Mills, S.J. (2013) Chiral edge-shared octahedral chains in liskear-dite, [(Al,Fe)32(AsO4)18(OH)42(H2O)22]-52H2O, an open framework mineral with a pharmacoalumite-related structure. Mineralogical Magazine, 77,3125–3135.CrossRefGoogle Scholar
Grey, I.E., Kampf, A.R., Price, J.R. and MacRae, C.M. (2014a) Bettertonite, IMA 2014-074. CNMNC Newsletter No. 23, February 2015, page 55; Mineralogical Magazine, 79, 51—58.Google Scholar
Grey, I.E., Mumme, W.G., Price, J.R., Mills, S.J., MacRae, C.M. and Favreau, G. (2014b) Ba-Cu ordering in bariopharmacoalumite-Q2a2b2c from Cap Garonne, France. Mineralogical Magazine, 78, 851–860.CrossRefGoogle Scholar
Grey, I.E., Betterton, J., Kampf, A.R., Price, J.R. and MacRae, C.M. (2015a) Penberthycroftite, IMA 2015-025. CNMNC Newsletter No. 26, August 2015, page 943; Mineralogical Magazine, 79, 941–947.Google Scholar
Grey, I.E., Kampf, A.R., Price, J.R. and MacRae, C.M. (2015b) Bettertonite, [Al6(AsO4)3(OH)9(H2O)5]-11H2O, a new mineral from the Penberthy Croft mine, St. Hilary, Cornwall, UK, with a structure based on polyoxometalate clusters. Mineralogical Magazine, 79, 1849–1858.CrossRefGoogle Scholar
Laugier, J. and Bochu, B. (2000) LMGP-Program for the Interpretation of X-ray Experiments. INPG/ Laboratoire des Matériaux et du Génie Physique. St Martin d'Heres, France.Google Scholar
Libowitzky, E. (1999) Correlation of O-H stretching frequencies and O-H-0 hydrogen bond lengths in minerals. Pp. 103-115 in: Hydrogen Bond Researc.(P. Schuster and W Mikenda, editors). Springer-Verlag Wien.Google Scholar
Majzlan, J., Alpers, C.N., Koch, C.B., McCleskey, R.B., Myneni, S.C.B. and Neil, J.M. (2011) Vibrational, X-ray absorption, and Mossbauer spectra of sulphate minerals from the weathered massive sulphide deposit at iron Mountain, California. Chemical Geology, 284, 296–305.CrossRefGoogle Scholar
Mandarino, J.A. (1981) The Gladstone-Dale relationship: Part IV The compatibility concept and its application. The Canadian Mineralogist, 19, 441–450.Google Scholar
Nakamoto, K. (1970) Infrared Spectra of Inorganic and Coordination Compounds. Wiley-Interscience, New York, 338 pp.Google Scholar
Petricek, Vand Dušek, M. (2006) JANA2006. Structure Determinations Software Programs.Institute of Physics, Academy of Sciences of the Czech Republic, Prague.Google Scholar
Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112—122.Google Scholar
Taylor, R. (2011) Gossans and Leached Cappings Field Assessment. Springer Verlag, Heidelberg, Germany, 146pp.CrossRefGoogle Scholar
Vansant, F.K., van der Veken, B.J. and Dessyn, H.O. (1973) Vibrational analysis of arsenic acid and its anions. 1. Description of the Raman spectra. Journal of Molecular Structure, 15, 425–4-37.CrossRefGoogle Scholar
Visser, J.W.(1969) A fully automated program for finding the unit cell from powder data. Journal of Applied Crystallography, 2, 89.CrossRefGoogle Scholar
Walenta, K (1983) Bulachit, ein neues Aluminiumarsenatmineral von Neubulach im nordli-chen Schwarzwald. Aufschluss, 34, 445—451.Google Scholar