N. Jb. Miner. Mh. Jg. 2002 (4) 160–168 Stuttgart, April 2002 Cattiite, Mg3(PO4)2 · 22H2O, a new mineral from Zhelezny Mine (Kovdor Massif, Kola Peninsula, Russia) Sergey N. Britvin, St. Petersburg, Giovanni Ferraris, Gabriella Ivaldi, Torino, Alla N. Bogdanova, Apatity, and Nikita V. Chukanov, Chernogolovka With 1 figure and 1 table Britvin, S. N., Ferraris, G., Ivaldi, G., Bogdanova, A. N. & Chukanov, N. V. (2002): Cattiite, Mg3(PO4)2 · 22H 2O, a new mineral from Zhelezny Mine (Kovdor Massif, Kola Peninsula, Russia). – N. Jb. Miner. Mh. 2002 (4): 160 –168; Stuttgart. Abstract: Cattiite, Mg3(PO4)2 · 22H 2O, is a new mineral from Zhelezny (Iron) Mine (Kovdor carbonatite massif, Kola Peninsula, Russia). It appears as crystalline masses up to 1.5 cm in size filling up cavities of dolomite carbonatite. Associated minerals are dolomite, bakhchisaraitsevite, nastrophite, magnetite, sjogrenite and carbonate – fluorapatite. Rare {001} tabular crystals are observed within the masses. Colourless, transparent. Lustre vitreous with pearly sheen on cleavage fractures. Perfect {001} cleavage. Brittle; Moh’s hardness 2. D(meas) 1.65(2) g/cm3, D(calc) 1.640(1) g/cm3. In immersion liquids cattiite is colourless and non-pleochroic. Biaxial ( – ), a 1.459(1), b 1.470(1), g 1.470(1), 2V(meas) 25(5)Ê for l 589 nm; weak dispersion r < v. Optical orientation: XÙ[001] = 80Ê , YÙ[100] = 10Ê , Z ^ [001]; optical axis plane close to the cleavage plane. IR spectrum (the strongest bands are underlined): 3490, 3390, 3050, 2410, 2102, 1665, 1602, 1055, 1006, 900, 805, 727, 557 cm –1. Chemical analysis (wet): MgO 18.0, FeO 0.1, P2O5 21.8, H2O 60.8, total 100.7 wt.%. Empirical formula (O = 30): (Mg2.92 Fe0.01)S2.93 P2.01O7.955 · 22.055H 2O. Simplified formula Mg3(PO4)2 · 22H 2O. Easily soluble in cool 10 % HCl. Dehydration begins over 40 Ê C. Triclinic P 1̄, a 6.932(2), b 6.925(3), c 16.154(5) Å, a 82.21(4), b 89.70(4), g 119.51(3)Ê , V 666.3(3) Å3 from X-ray powder and singlecrystal diffractometry, Z = 1. Interplanar spacings (Å), intensity and hkl for the strongest lines in the X-ray powder diffraction pattern: 7.98(100)(002), 5.32(63)(003), 3.190(45)(005), 2.896(33)(202), 2.867(30)( – 222), 2.728(32)(1–15), 2.658(37)(006). Cattiite corresponds to the synthetic polytype 1A2 of Mg3(PO4)2 · 22H 2O; the polytype 1A1 is known for synthetic material only. It is DOI: 10.1127/0028-3649/2002/2002-0160 0028-3649/02/2002-0160 $ 2.25 ã 2002 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart Cattiite, a new mineral 161 named in honour to Michele Catti (b. 1945), Professor of Physical Chemistry, University of Milano Bicocca (Italy). Key words: cattiite, new mineral, phosphate, Kola Peninsula, Kovdor massif. Introduction The veins of dolomite carbonatites exposed in the Zhelezny (Iron) Mine (Kovdor massif, Kola Peninsula, Russia) are enriched in late hydrothermal Mg-rich phosphates as kovdorskite, girvasite, rimkorolgite, strontiowhitlockite, krasnovite, juonniite, bakhchisaraitsevite, bobierrite and collinsite (Kapustin et al. 1980, Britvin et al. 1990, Britvin et al. 1991, Britvin et al. 1995, Liferovich et al. 2000). During field work in Summer 1999, an unknown mineral has been found in the same association and tentatively identified as Mg3(PO4)2 · 22H 2O, a high hydrate magnesium orthophosphate known as synthetic phase since 19th century (Haushofer 1882, Pietsch 1938). Structural studies by Schroeder et al. (1978) and Catti et al. (1981) revealed the existence of two polytypes named Mg3(PO4)2 · 22H2O – I and Mg3(PO4)2 · 22H 2O – II, respectively. Both polytypes are triclinic (see Crystallography) and according to the nomenclature of polytypes (Guinier et al. 1984) shall here be indicated, in the same order, as Mg3(PO4)2 · 22H 2O –1A1 and Mg3(PO4)2 · 22H2O–1A2, where the index 1 and 2 applied to A (for anorthic) indicates the order of discovery. The characterisation of the new phosphate from Kovdor showed that it corresponds to Mg3(PO4)2 · 22H 2O –1A2 polytype. Both the mineral and the name have been approved (2000 – 032) by the Commission on New Minerals and Mineral Names (CNMMN) of the International Mineralogical Association (IMA). The mineral is named cattiite, in honour to Michele Catti (b. 1945), Professor of Physical Chemistry, University of Milano Bicocca (Italy), for his contributions to the crystal chemistry of hydrated oxysalts. The holotype specimen of cattiite is deposited at the Mineralogical Museum, Department of Mineralogy, Saint-Petersburg State University, catalogue number 1/18618. Occurrence and physical properties Cattiite has been found in several cm-sized cavities within a 20 – 40 cm thick vein of dolomite carbonatites; the vein cross-cuts forsterite – magnetite 162 S. N. Britvin et al. ore at the bottom of the Zhelezny Mine quarry. Associated minerals are nastrophite, bakhchisaraitsevite, sjogrenite, magnetite, and carbonate – fluorapatite. The mineral occurs as masses up to 1.5 cm in size filling up free space of cavities and interstices of associated minerals. The masses of cattiite usually contain single-crystals which sometime show {001} as dominant form. Cattiite is colourless and transparent, with {001} perfect cleavage and uneven fracture in other directions. Lustre is vitreous, with gypsum-like pearly sheen on cleavage planes; brittle; Mohs’ hardness 2. D(obs) = 1.65(2) g/cm3 (floating in CHBr3 – C5H11OH solution), D(calc) = 1.64 g/ cm3 for the ideal formula and unit cell given below. In immersion liquids, the mineral is colourless and non-pleochroic. Biaxial ( – ), a = 1.459(1), b = 1.470(1), g = 1.470(1), 2V(meas) = 25(5)Ê for l 589 nm; 2V(calc) = 0Ê , a value strongly influenced by even a slight difference between b and g. Optical orientation: X Ù [001] = 80Ê , Y Ù [100] = 10Ê , Z ^ [001] (optical axes plane close to the cleavage plane). Dispersion weak, r < v. IR-spectroscopy and chemical composition The infrared (IR) absorption spectrum of cattiite (Fig. 1) was obtained using a Perkin-Elmer FTIR spectrophotometer with the sample dispersed in mineral oil (nuyol) at 12 Ê C and 90 % relative air humidity. The absorption bands of the oil were subtracted from the spectrum. The strongest and broad Fig. 1. IR spectrum of cattiite. Cattiite, a new mineral 163 bands in the cattiite IR spectrum are observed in the region of OH stretching vibrations of H2O molecules, at 3490, 3390 (strongest band) and 3050 cm –1. A weak broad band at 2410 cm –1 and a weak narrow band at 2102 cm –1 correspond to the stretching vibrations of the PO – H + d bond and free H + ions respectively. Taking into account this fact and lack of octahedral cations in the empirical formula (0.07 atoms per formula unit, see below), we can suggest that a minor part of the phosphate ions is involved into the equilibrium H + + (PO4)3 – « (HPO4)2 – . The bands at 1665 and 1602 cm –1 correspond to in-plane H – O – H bending vibrations of at least two different types of water molecules. The other bands are assigned to asymmetrical (at 1055 and 1006 cm –1) and symmetrical (900 cm –1) stretching vibrations of (PO4)3 – , out-of-plane vibrations of H2O (805, 727 cm –1), and bending vibrations (PO4)3 – (557cm –1). According to the IR data, cattiite does not contain borate, carbonate or nitrate anions as well as (NH4) + cations and C – H bonds. Due to its high hydration, cattiite is unstable under heating. Thermal studies by Bakaev et al. (1974) showed that synthetic Mg3(PO4)2 · 22H 2O is partially dehydrated above 70 Ê C. According to our observations, partial dehydration of cattiite begins at 40 – 60 Ê C, depending probably on the relative air humidity. The product of partial dehydration is a white powder whose X-ray powder diffraction pattern is similar to that of bobierrite, Mg3(PO4)2 · 8H 2O. Cattiite is easily soluble in diluted cold 10 % HCl and looses water under vacuum when studied by electron microprobe. The following chemical composition (wt.%) was determined by wet analysis from 243.5 mg of sample: MgO 18.0, FeO 0.1, P2O5 21.8, H2O 60.8 (weight loss at 1000 Ê C), total 100.7. No measurable amounts of other elements were detected by ICP. The empirical formula calculated on the basis of 30 oxygen atoms is (Mg2.92 Fe0.01)S2.93P2.01O7.955 · 22.055H 2O; it well corresponds to the ideal formula Mg3(PO4)2 · 22H 2O. Crystallography As mentioned above, two polytypes of Mg3(PO4)2 · 22H 2O are known. Both phases are triclinic with very close cell parameters and their crystal structures, as discussed by Catti et al. (1981), are very close too. In fact, the structures of both polytypes are based on isolated PO4 tetrahedra and Mg(H2O)6 octahedra which are connected by hydrogen bonds. A part minor features, in both structures a (001) sheet of octahedra plus a sheet consisting 164 S. N. Britvin et al. of octahedra and tetrahedra form a polar (001) slab which is duplicated by a centre of symmetry to form a layer with thickness corresponding to the c parameter. Two different centres of symmetry locally connect two polar (slightly modified) (001) slabs; consequently, two different one-layer polytypes can be formed. The cell parameters of the two polytypes are: – a = 6.902, b = 6.961, c = 15.982 Å, a = 87.66, b = 94.78, 147 = 119.19Ê (space group P 1̄; Z = 1) for the polytype 1A1 described by Schroeder et al. (1978) (original cell transformed by 100/01̄0/00 1̄); – a = 6.937, b = 6.932, c = 16.132 Å, a = 82.15, b = 89.72, g = 119.49Ê (space group P 1̄; Z = 1) for the polytype 1A2 described by Catti et al. (1981). A study by X-ray single-crystal diffractometry of cattiite showed that its cell [a = 6.932(2), b = 6.925(3), c = 16.154(5) Å, a = 82.21(4), b = 89.70(4), g = 119.51(3)Ê , V = 666.3 (3) Å3, Z = 1, space group P 1̄] corresponds to that published by Catti et al. (1981) for the polytype 1A2. Identity of composition between natural and synthetic phases and the low quality of the diffraction shown by our crystals of cattiite (which easily loose water) suggested the uselessness of repeating a structural refinement. Table 1 shows (i) the observed and calculated X-ray powder diffraction patterns of cattiite and of the corresponding synthetic polytype 1A2 taken from Catti et al. (1981); (ii) calculated data for the synthetic polytypes 1A1. The data of synthetic polytypes are limited to d = 2.4 Å. The structural information for calculation is taken from Catti et al. (1981) for 1A2 and from Schroeder et al. (1978) for 1A1. The X-ray powder diffraction pattern of cattiite was acquired using a DRON 2 diffractometer (CoK a, quartz monochromator, 20kV, 30mA, scan speed 0.5Ê /min). The indexing of the experimental patterns was done by comparing observed (Iobs) with calculated diffraction intensities (Icalc) and observed (dobs) with calculated (dcalc) interplanar distances. Refined cell parameters from the powder diffraction data of cattiite are reported above. Note that without single-crystal data, the powder diffraction pattern of cattiite could not be easily identified with that of one of the two described polytpes; in fact, as expected in general for polytypes, very similar patterns are shown by the two polytypes. The weak reflection with dobs = 4.83 Å cannot be indexed by the cell of cattiite but corresponds to one of the strongest lines of Mg3(PO4)2 · 22H 2O –1A1. The intensity of this reflection depends on the sample preparation (i.e. by grinding with water or with ethanol) and one can suppose that some formation of polytype 1A1 depends on the grinding procedure. Cattiite, a new mineral 165 Table 1. X-ray powder diffraction data for cattiite (CoKa radiation, l = 1.78901 Å, quartz monochromator). Observed data for synthetic 1A2 and all data for 1A2 are limited to dcalc = 2.371 Å. See text for further explanation. Cattiite Iobs dobs Synthetic 1A2 Iobs dobs 100 22 7 17 7.98 6.01 5.88 5.80 50 7.97 35 6.03 6 63 2 16 27 5 8 26 4 26 23 4 2 11 5.45 5.32 5.18 5.00 4.96 4.83 4.62 4.44 4.32 4.13 3.99 3.83 3.59 3.46 10 5.47 35 5.32 9 10 10 5 45 3.44 3.39 3.35 3.26 3.19 2 3.079 5 3.005 10 5.75 40 4.96 5 4.63 40 4.12 15 3.985 10 3.467 5 3.266 40 3.186 10 3.005 5 2.977 15 2.902 15 2.905 33 2.896 20 2.901 30 2.867 100 2.865 Synthetic 1A1 Icalc dcalc hkl Icalc dcalc 100 49 30 64 7.97 6.01 5.89 5.79 002 100 011 101 10 53 10 30 58 5.45 5.32 5.18 5.01 4.96 1-11 003 012 102 – 112 2 97 11 42 13 3 4 5 11 18 24 30 5 9 23 16 6 4 6 5 7 11 11 78 77 4.62 4.44 4.32 4.13 3.99 3.83 3.59 3.47 3.46 3.43 3.39 3.35 3.26 3.20 3.19 3.18 3.079 3.006 3.000 2.975 2.974 2.910 2.898 2.894 2.867 10-2 01-2 013 – 113 004 1-13 014 2-10 104 1-20 2-11 112 1-21 1-14 005 2-12 – 123 200 201 020 2-2-1 20-1 2-1-3 202 – 222 95 7.96 92 6.01 11 25 18 50 5.72 5.68 5.46 5.31 57 4.95 62 4.83 45 4.64 46 4.12 21 4.00 18 3.84 25 3 4 20 34 18 9 26 3.48 3.45 3.44 3.39 3.31 3.26 3.21 3.19 Cattiite hkl Iobs dobs 002 4 100 13 6 111 011 5 11-1 2 003 16 3 1 112 4 01-2 2 10-2 2 113 01-3 10-3 120 1-11 104 1-1-1 21-1 1-12 11-4 005 2 3 4 6 2 4 7 4 4 4 6 3.065 21-2 2 6 3.005 200 1 15 2.985 021 4 11 16 2.967 123 74 2.914 20-1 4 7 2.898 115 1 7 2.893 22-1 3 86 2.861 222 2 Synthetic 1A2 Icalc dcalc 2.363 25 2.310 31 2.286 13 5 2.265 5 2.233 3 2.184 18 2.167 7 2.112 1 2.101 10 2.077 1 1 2.063 2 2 2.036 3 2.024 5 5 1.994 7 1.967 14 1.946 5 1.938 2 13 1.913 10 1.882 6 5 1.842 6 1.821 10 1.791 6 1.773 1 1.746 12 1.731 17 5 1.721 7 1.700 1 1.675 3 1.662 1 2.362 2.309 2.285 2.267 2.265 2.234 2.185 2.165 2.113 2.101 2.079 2.076 2.065 2.064 2.038 2.023 2.001 1.992 1.966 1.946 1.936 1.914 1.914 1.881 1.881 1.841 1.826 1.790 1.777 1.744 1.731 1.723 1.719 1.702 1.673 1.660 hkl 1-16 – 204 205 2-2-5 3-20 3-21 – 117 – 312 21-2 2-25 206 1-17 – 234 – 313 117 01-7 032 – 324 027 3-1-4 1-1-8 2-26 20-6 2-2-7 3-15 216 2-3-6 11-7 019 221 2-4-1 4-21 2-2-8 3-26 224 4-30 166 S. N. Britvin et al. Table 1. Continued. Cattiite Iobs dobs 22 4 32 37 2.845 2.795 2.728 2.658 9 2.590 7 2.526 6 2.506 Synthetic 1A2 Iobs dobs 90 2.846 10 2.795 45 2.658 15 2.523 4 2.438 4 2.371 Icalc dcalc 69 6 29 29 19 38 11 8 7 10 12 2.844 2.796 2.728 2.658 2.653 2.590 2.521 2.503 2.442 2.437 2.371 Synthetic 1A1 hkl Icalc dcalc Cattiite hkl Iobs dobs 0-21 100 2.839 02-2 023 6 2.821 015 1-15 32 2.729 11-5 006 29 2.654 006 02-2 18 2.637 023 024 4 2.637 02-3 2-23 20 2.537 20-3 204 10 2.523 22-3 1-24 10 2.487 204 02-3 27 2.416 024 025 3 2.362 11-6 2 1.652 3 1.630 1 1 1 3 3 2 3 1.614 1.605 1.578 1.450 1.435 1.412 1.377 Synthetic 1A2 Icalc dcalc 3 6 2 3 8 1 1 1 2 1 5 hkl 1.651 3-40 1.649 4-23 1.631µ 11-8 1.630 1-28 1.612 4-32 1.606 0110 1.577 2-2-9 1.444 4-16 1.434 4-4-4 1.414 3-2-9 1.377 04-3 depends on the sample preparation (i.e. by grinding with water or with ethanol) and one can suppose that some formation of polytype 1A1 depends on the grinding procedure. Conclusions Preparations of synthetic Mg3(PO4)2 · 22H 2O (Pietsch 1938, Bakaev et al. 1974, Schroeder et al. 1978, Catti et al. 1981) do not differ for the two polytypes and were carried out in cold water solutions at 5 – 25 Ê C; presumably the appearance of one more than another polytype depends on subtle conditions. We suggest that in the Zhelezny mine of Kovdor massif, cattiite formed from cold Mg-rich phosphate solutions during post-hydrotermal stage of carbonatite formation. Under heating, as mentioned above, dehydration of cattiite does not appear below about 40 Ê C; therefore the species can be considered a stable phase under the mine conditions. Acknowledgements We gratefully acknowledge Dr. M. Yagovkina (Mekhanobr-Analyt Analytical Centre, St. Petersburg) for collecting the X-ray powder diffraction pattern of cattiite. This work was carried out by S.N.B. with the financial support of the grant INTAS OPEN-97-0722. G.F. and G.I. contribution is in the framework of 40 % MURST and CNR projects. Cattiite, a new mineral 167 References Bakaev, A. Y., Dzisko, V. A., Karakchiev, L. G., Moroz, E. M., Kustova, G. N. & Tsikoza, L. T. (1974): Influence of preparation conditions on physico-chemical properties of phosphates. II. Phase composition and relative surface value of magnesium phosphates. – Kinetics and Catalysis 15: 1275 –1282. (in Russian). Britvin, S. N., Pakhomovskii, Y. A., Bogdanova, A. N., Khomyakov, A. P. & Krasnova, N. I. (1995): Rimkorolgite, (Mg,Mn) 5(Ba,Sr,Ca)(PO4)4 · 8H 2O, a new mineral. – Zap. Vses. Mineral. Obsch. 124: 90 – 95. (in Russian). Britvin, S. N., Pakhomovskii, Y. A., Bogdanova, A. N. & Skiba, V. I. (1991): Strontiowhitlockite, Sr9Mg(PO3OH)(PO4)6, a new mineral species from the Kovdor deposit, Kola-Peninsula, USSR. – Can. Mineral. 29: 87– 93. Britvin, S. N., Pakhomovskii, Y. A., Bogdanova, A. N. & Sokolova, E. V. (1990): Girvasite, a new carbonate – phosphate of sodium, calcium and magnesium. – Mineral. Zhurnal. 12: 79 – 83. (in Russian). Catti, M., Franchini-Angela, M. & Ivaldi, G. (1981): A case of polytypism in hydrated oxysalts: the crystal structure of Mg3(PO 4)2 · 22H 2O– II. – Z. Kristallogr. 155: 53 – 64. Ï Guinier, A., Bokij, G. B., Boll-Dornberger, K., Cowley, J. M., Durovi cÏ , S., Jagodzinski, H., Krishna, P., De Wolff, P. M., Zvyagin, B. B., Cox, D. E., Goodman, P., Hahn, Th., Kuchitsu, K. & Abrahams, S. C. (1984): Nomenclature of polytype structures. Report of the International Union of Crystallography Ad hoc Committee on the Nomenclature of Disordered, Modulated and Polytype Structures. – Acta Crystallogr. A 40: 399 – 403. Haushofer, K. (1882): Kristallographische Untersuchungen. – Z. Kristallogr. 6: 113 –141. Kapustin, Yu. L., Bykova, A. V. & Pudovkina, Z. V. (1980): Kovdorskite, a new mineral. – Zap. Vses. Mineral. Obsch. 109: 341– 347. (in Russian). Liferovich, R. P., Pakhomovsky, Ya. A., Yakubovich, O. V., Massa, W., Laajoki, K., Gehör, S., Bogdanova, A. N. & Sorokht ina, N. V. (2000): Bakhchisaraitsevite, Na2Mg5[PO4]4 · 7H 2O, a new mineral from hydrothermal assemblages related to phoscorite – carbonatite complex of the Kovdor massif, Russia. – N. Jb. Miner. Mh. 2000: 402 – 418. Pietsch, E. (ed.) (1938): Gmelin’s Handbuch der Anorganischen Chemie. 8 Auflage. System-Nummer 27: Magnesium. Teil B, Lieferung 3. Berlin. Schroeder, L. W., Mathew, M. & Brown, W. E. (1978): XO4n – ion hydration. The crystal structure of Mg3(PO4)2 · 22H 2O. – J. Phys. Chem. 82: 2335 – 2340. Received: October 2, 2001. 168 S. N. Britvin et al. Authors’ addresses: Sergey N. Britvin, Department of Mineral Deposits, St. Petersburg State University, University Emb. 7/9, St. Petersburg 199034, Russia. Giovanni Ferraris, Gabriella Ivaldi, Dipartimento di Scienze Mineralogiche e Petrologiche, UniversitÞ di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy; e-mail: ferraris@dsmp.unito.it. Alla N. Bogdanova, Geological Institute, Kola Science Center of Russian Academy of Sciences, Fersman Street 14, Apatity 184200, Russia. Nikita V. Chukanov, Institute of Chemical Physics Problems RAS, Chernogolovka, Moscow region, 14232, Russia. Correspondence author: Prof. Giovanni Ferraris (address above). View publication stats