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Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile

Published online by Cambridge University Press:  02 January 2018

Anthony R. Kampf ,
Barbara P. Nash ,
Maurizio Dini  and
Arturo Molina A. Donoso
Anthony R. Kampf*
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
Barbara P. Nash
Affiliation:
Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
Maurizio Dini
Affiliation:
Pasaje San Agustin 4045, La Serena, Chile
Arturo Molina A. Donoso
Affiliation:
Los Algarrobos 2986, Iquique, Chile
*
*E-mail: [email protected]
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Abstract

The new mineral gajardoite (IMA2015-040), KCa0.5As3+4O6Cl2·5H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with native arsenic, arsenolite,chongite, talmessite and torrecillasite. Gajardoite occurs as hexagonal plates up to ∼100 μm in diameter and 5 μm thick, in rosette-like subparallel intergrowths. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is ∼1½, tenacity is brittleand fracture is irregular. Cleavage is perfect on {001}. The measured density is 2.64 g/cm3 and the calculated density is 2.676 g/cm3. Optically, gajardoite is uniaxial (–) with ω = 1.780(3) and ε = 1.570(5) (measured in white light). The mineral is very slowly soluble in H2O and slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (K0.77Ca0.71Na0.05Mg0.05)∑1.58As4O11Cl1.96H9.62.Gajardoite is hexagonal, P6/mmm, a = 5.2558(8), c = 15.9666(18) Å, V = 381.96(13) Å3 and Z = 1. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 16.00(100)(001), 5.31(48)(003),3.466 (31)(103), 3.013(44)(104), 2.624(51)(006,110,111), 2.353(36)(113), 1.8647(21)(116,205) and 1.4605(17) (119,303,216). The structure, refined to R1 = 3.49% for 169 Fo > 4σF reflections, contains two types of layers. One layer of formulaKAs3+4O6Cl2 consists of two neutral As2O3 sheets, between which are K+ cations and on the outside of which are Cl– anions. This layer is topologically identical to a slice of the lucabindiite structureand similar to a slice of the torrecillasite structure. The second layer consists of an edge-sharing sheet of Ca(H2O)6 trigonal pyramids with isolated H2O groups centred in the hexagonal cavities in the sheet.

Keywords

gajardoitenew mineralarsenitecrystal structurelucabindiitetorrecillasiteTorrecillas mineChile
Type
Research Article
Information
Mineralogical Magazine , Volume 80 , Issue 7 , December 2016 , pp. 1265 - 1272
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2016

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References

Brese, N.E. and O'Keeffe, M. (1991) Bond-valence parameters for solids. Acta Crystallographica,B47, 192–197.CrossRefGoogle Scholar
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters from a systematic analysis of the inorganic crystal structure database. Acta Crystallographica,B41, 244–247.CrossRefGoogle Scholar
Burla, M.C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G.L., Giacovazzo, C., Mallamo, M., Mazzone, A., Polidori, G and Spagna, R. (2012) SIR2011: a new package for crystal structure determination and refinement. Journal of Applied Crystallography, 45, 357–361.CrossRefGoogle Scholar
Cameron, E.M., Leybourne, M.I. and Palacios, C. (2007) Atacamite in the oxide zone of copper deposits in northern Chile: involvement of deep formation waters? Mineralium Deposita, 42, 205–218.CrossRefGoogle Scholar
Garavelli, A., Mitolo, D., Pinto, D. and Vurro, F. (2013) Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole mineral from the “La Fossa” crater at Vulcano, Aeolian Islands, Italy. American Mineralogist, 98, 470—477.CrossRefGoogle Scholar
Gutiérrez, H. (1975) Informe sobre una rápida visita a la mina de arsénico nativo, Torrecillas. Instituto de Investigaciones Geológicas, Iquique, Chile Google Scholar
Higashi, T. (2001) ABSCOR. Rigaku Corporation, Tokyo.Google Scholar
Kampf, A.R., Sciberras, M.J, Williams, P.A., Dini, M. and Molina Donoso, A.A. (2013a) Leverettite from the Torrecillas mine, Iquique Provence, Chile: the Co-analogue of herbertsmithite Mineralogical Magazine, 77,3047–3054.CrossRefGoogle Scholar
Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2013b) Magnesiokoritnigite, Mg(AsO3OH)-H2O, from the Torrecillas mine, Iquique Province, Chile: the Mg-analogue of koritnigite. Mineralogical Magazine, 77,3081–3092.CrossRefGoogle Scholar
Kampf, A.R., Sciberras, M.J., Leverett, P., Williams, P.A., Malcherek, T., Schlüter, J., Welch, M.D., Dini, M. and Molina Donoso, A.A. (2013c) Paratacamite-(Mg), Cu3(Mg,Cu)Cl2(OH)6: a new substituted basic copper chloride mineral from Camarones, Chile. Mineralogical Magazine, 77,3113–3124.CrossRefGoogle Scholar
Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2014a) Torrecillasite, Na(As,Sb)3+4O6Cl, a new mineral from the Torrecillas mine, Iquique Province, Chile: description and crystal structure. Mineralogical Magazine, 78, 747–755.CrossRefGoogle Scholar
Kampf, A.R., Mills, S.J., Hatert, F., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2014b) Canutite, NaMn3[AsO4][AsO2(OH)2], a new protonated alluau-dite-group mineral from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine, 78, 787–795.CrossRefGoogle Scholar
Kampf, A.R., Nash, B., Dini, M. and Molina Donoso, A.A. (2015) Gajardoite, IMA 2015–2040. CNMNC Newsletter No. 26, August 2015, page 947; Mineralogical Magazine, 79, 941–947.Google Scholar
Kampf, A.R., Nash, B.P., Dini, M. and Molina Donoso, A.A. (2016) Chongite, Ca3Mg2(AsO4)2(AsO3OH)2.4H2O, a new arsenate member of the hureaulite group from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine, 80, 1255–1263.CrossRefGoogle Scholar
Mandarino, J.A. (2007) The Gladstone-Dale compatibility of minerals and its use in selecting mineral species for further study. The Canadian Mineralogist, 45, 1307–1324.CrossRefGoogle Scholar
Mortimer, C., Saric, N. and Cáceres, R. (1971) Apuntes sobre algunas minas de la región costera de la provincia de Tarapacá.Instituto de Investigaciones Geológicas, Santiago de Chile, Chile.Google Scholar
Pimentel, F. (1978) Proyecto Arsenico Torrecillas.Instituto de Investigaciones Geológicas, Iquique, Chile.Google Scholar
Pouchou, J.-L. and Pichoir, F. (1991) Quantitative analysis of homogeneous or stratified microvolumes applying the model ‘PAP.’ Pp. 3l-75 in: Electron Probe Quantitatio.(K.F.J. Heinrich and D.E. Newbury, editors). Plenum Press, New York.Google Scholar
Sheldrick, G.M. (2015) Crystal structure refinement with SHELXL. Acta Crystallographica,C71, 3–8.Google Scholar
Wood, R.M. and Palenik, G.J. (1999) Bond valence sums in coordination chemistry using new R0 values. Potassium-oxygen complexes. Inorganic Chemistry, 38, 1031–1034.Google Scholar