Cattiite, Mg₃(PO₄)₂·22H₂O, a new mineral from Zhelezny Mine (Kovdor Massif, Kola Peninsula, Russia)

Authors: Britvin, Sergey N.; Ferraris, Giovanni; Ivaldi, Gabriella; Bogdanova, Alla N.; Chukanov, Nikita V.

Source: Neues Jahrbuch für Mineralogie - Monatshefte, Volume 2002, Number 4, 1 April 2002 , pp. 160-168(9)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

Cattiite, Mg₃(PO₄)₂·22H₂O, 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 (-), alpha

1.459(1),

1.470(1),

1.470(1), 2V(meas) 25(5) ring

for

589 nm; weak dispersion r < v. Optical orientation: X and

[001] = 80 ring

, Y

[100] = 10 ring

, 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, 557cm^-1. Chemical analysis (wet): MgO 18.0, FeO 0.1, P₂O₅ 21.8, H₂O 60.8, total 100.7wt.%. Empirical formula (O = 30): (Mg_2.92Fe_0.01)_2.93P_2.01O_7.955 · 22.055H₂O. Simplified formula Mg₃(PO₄)₂ · 22H₂O. Easily soluble in cool 10% HCl. Dehydration begins over 40 ring

C. Triclinic P 1¯, a 6.932(2), b 6.925(3), c 16.154(5) Å, alpha

82.21(4),

89.70(4),

119.51(3)

, V 666.3(3) Å³ from X-ray powder and single-crystal 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 · 22H₂O; the polytype 1A1 is known for synthetic material only. It is named in honour to Michele Catti (b. 1945), Professor of Physical Chemistry, University of Milano Bicocca (Italy).

Keywords: CATTIITE; NEW MINERAL; PHOSPHATE; KOLA PENINSULA; KOVDOR MASSIF

Document Type: Regular paper

DOI: http://dx.doi.org/10.1127/0028-3649/2002/2002-0160

Publication date: 2002-04-01