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Antofagastaite, Na2Ca(SO4)2·1.5H2O, a new mineral related to syngenite

  • Igor V. Pekov (a1), Vadim M. Kovrugin (a2) (a3), Oleg I. Siidra (a2) (a4), Nikita V. Chukanov (a5), Dmitry I. Belakovskiy (a6), Natalia N. Koshlyakova (a1), Vasiliy O. Yapaskurt (a1), Anna G. Turchkova (a1) and Gerhard Möhn (a7)...


The new mineral antofagastaite, ideally Na2Ca(SO4)2·1.5H2O, was found in the oxidation zone of sulfide–quartz veins at the abandoned Coronel Manuel Rodríguez mine, Mejillones, Antofagasta Province, Antofagasta Region, Chile. It is associated with sideronatrite, metasideronatrite, aubertite, gypsum, ferrinatrite, glauberite, amarillite and an unidentified Fe phosphate. Antofagastaite occurs as prismatic crystals up to 0.5 mm × 1 mm × 5 mm, elongated along [010], typically combined in open-work aggregates up to 1 cm across. Antofagastaite is transparent and colourless, with vitreous lustre. It is brittle; the Mohs’ hardness is ca 3. Cleavage is distinct on (001). Dmeas. is 2.42(1) and Dcalc. is 2.465 g cm−3. Antofagastaite is optically biaxial (–), α = 1.489(2), β = 1.508(2), γ = 1.510(2) and 2Vmeas. = 40(10)°. The IR spectrum is reported. Chemical composition (wt.%, electron microprobe, H2O determined by gas chromatography) is: Na2O 20.85, CaO 17.42, SO3 52.56, H2O 7.93, total 98.76. The empirical formula (based on 8 O atoms belonging to sulfate anions per formula unit with all H belonging to H2O molecules) is Na2.06Ca0.95S2.01O8·1.35H2O. Antofagastaite is monoclinic, P21/m, a = 6.4596(4), b = 6.8703(5), c = 9.4685(7) Å, β = 104.580(4)°, V = 406.67(5) Å3 and Z = 2. The strongest reflections of the powder XRD pattern [d, Å (I, %) (hkl)] are: 9.17 (100) (001), 5.501 (57) (011), 3.437 (59) (020), 3.058 (43) (003), 2.918 (50) (2¯11), 2.795 (35) (013) and 2.753 (50) (121, 201). The crystal structure was solved based on single-crystal X-ray diffraction data, R1 = 5.71%. The structure of antofagastaite consists of ordered and disordered blocks and is related to syngenite K2Ca(SO4)2·H2O. Incorporation of additional H2O molecules in the syngenite-type structure results in disorder of the one of the two tetrahedral sulfate groups occurring in antofagastaite. In addition to the above-reported type material, antofagastaite together with syngenite and blödite occurs in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia.


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*Author for correspondence: Igor V. Pekov, Email:


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Associate Editor: František Laufek



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Anthony, J.W., Bideaux, R.A., Bladh, K.W. and Nichols, M.C. (2003) Handbook of Mineralogy, Volume: V. Borates, Carbonates, Sulfates. Mineral Data Publishing, Tucson, 813 pp.
Araki, T. and Zoltai, T. (1967) Refinement of the crystal structure of a glauberite. American Mineralogist, 52, 12721277.
Ballirano, P., Belardi, G. and Maras, A. (2005) Refinement of the structure of synthetic syngenite K2Ca(SO4)2·H2O from X-ray powder diffraction data. Neues Jahrbuch für Mineralogie - Abhandlungen, 182, 1521.
Bokiy, G.B., Pal'chik, N.A. and Antipin, M.Y. (1978) More precise determination of syngenite crystal structure. Kristallografiya, 23, 257260 [in Russian].
Britvin, S.N., Dolivo-Dobrovolsky, D.V. and Krzhizhanovskaya, M.G. (2017) Software for processing the X-ray powder diffraction data obtained from the curved image plate detector of Rigaku RAXIS Rapid II diffractometer. Zapiski Rossiiskogo Mineralogicheskogo Obshchestva, 146, 104107 [in Russian].
Chukanov, N.V. (2014) Infrared Spectra of Mineral Species: Extended Library. Springer Verlag, Dordrecht, 1716 pp.
Corazza, Ε. and Sabelli, C. (1967) The crystal structure of syngenite, K2Ca(SO4)2·H2O. Zeitschrift für Kristallographie, 124, 398408.
Freyer, D., Reck, G., Bremer, M. and Voigt, W. (1999) Thermal behaviour and crystal structure of sodium-containing hemihydrates of calcium sulfate. Monatshefte für Chemie, 130, 11791193.
Gerakines, P.A., Schutte, W.A., Greenberg, J.M. and van Dishoeck, E.F. (1995) The infrared band strengths of H2O, CO and CO2 in laboratory simulations of astrophysical ice mixtures. Astronomy and Astrophysics, 296, 810818.
Leverett, P. and Williams, P.A. (2007) Unusual post-mining sulfates from the Peelwood and Lloyd mines, New South Wales, and a comment on wattevilleite. Australian Journal of Mineralogy, 13, 4146.
Libowitzky, E. (1999) Correlation of O–H stretching frequencies and O–H···O hydrogen bond lengths in minerals. Monatshefte für Chemie, 130, 10471059.
Mees, F., Hatert, F. and Rowe, R. (2008) Omongwaite, Na2Ca5(SO4)6·3H2O, a new mineral from recent salt lake deposits, Namibia. Mineralogical Magazine, 72, 13071318.
Mills, S.J., Kampf, A.R., Dini, M. and Molina, A. (2012) Die weltbesten Destinezit-Kristalle und andere seltene Sulfate von Mejillones, Chile. Mineralien-Welt, 23, 7381. (In German).
Palache, C. and Foshag, W.F. (1938) Antofagastite and bandylite, two new copper minerals from Chile. American Mineralogist, 23, 8590.
Palache, C., Berman, H. and Frondel, C. (1951) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837–1892. Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.
Palatinus, L. and Chapuis, G. (2007) SUPERFLIP – a computer program for the solution of crystal structures by charge flipping in arbitrary dimension. Journal of Applied Crystallography, 40, 786790.
Pekov, I.V., Koshlyakova, N.N., Zubkova, N.V., Lykova, I.S., Britvin, S.N., Yapaskurt, V.O., Agakhanov, A.A., Shchipalkina, N.V., Turchkova, A.G. and Sidorov, E.G. (2018) Fumarolic arsenates – a special type of arsenic mineralization. European Journal of Mineralogy, 30, 305322.
Pekov, I.V., Lykova, I.S., Agakhanov, A.A., Belakovskiy, D.I., Vigasina, M.F., Britvin, S.N., Turchkova, A.G., Sidorov, E.G. and Scheidl, K.S. (2019) New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XII. Zubkovaite, Ca3Cu3(AsO4)4. Mineralogical Magazine, 83,
Sabelli, C. and Trosti-Ferroni, R. (1985) A structural classification of sulfate minerals. Periodico di Mineralogia, 54, 146.
Sheldrick, G.M. (2015) Crystal structure refinement with SHELXL. Acta Crystallographica, C71, 38.
Slyusareva, M.N. (1969) Hydroglauberite, a new mineral of the hydrous sulfate group. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 98, 5962 [in Russian].
Vergouwen, L. (1981) Eugsterite, a new salt mineral. American Mineralogist, 66, 632636.


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Antofagastaite, Na2Ca(SO4)2·1.5H2O, a new mineral related to syngenite

  • Igor V. Pekov (a1), Vadim M. Kovrugin (a2) (a3), Oleg I. Siidra (a2) (a4), Nikita V. Chukanov (a5), Dmitry I. Belakovskiy (a6), Natalia N. Koshlyakova (a1), Vasiliy O. Yapaskurt (a1), Anna G. Turchkova (a1) and Gerhard Möhn (a7)...


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