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CARYOCHROITE, A NEW HETEROPHYLLOSILICATE MINERAL SPECIES RELATED TO NAFERTISITE, FROM THE LOVOZERO MASSIF, KOLA PENINSULA, RUSSIA

Pavel M. Kartashov^1,, Giovanni Ferraris^2,¶, Svetlana V. Soboleva³ and Nikita V. Chukanov⁴

¹ Institute of Geology of Ore Deposits, Mineralogy, Petrology and Geochemistry, Russian Academy of Sciences, IGEM, Russian Academy of Sciences, Staromonetnyi per. 35, RU-109017 Moscow, Russia
² Dipartimento di Scienze Mineralogiche e Petrologiche, Università di Torino, and Istituto di Geoscienze e Georisorse, CNR, Via Valperga Caluso, 35, I-10125 Torino, Italy
³ Institute of Geology of Ore Deposits, Mineralogy, Petrology and Geochemistry, Russian Academy of Sciences, IGEM, Russian Academy of Sciences, Staromonetnyi per. 35, RU-109017 Moscow, Russia, and Dipartimento di Scienze Mineralogiche e Petrologiche, Università di Torino, Via Valperga Caluso, 35, I-10125 Torino, Italy
⁴ Institute of Problems of Chemical Physics, RU-142432 Chernogolovka, Moscow Oblast, Russia

E-mail address: pmk{at}igem.ru

Caryochroite, a new mineral species, ideally (Na,Sr)₃(Fe³⁺,Mg)₁₀[Ti₂Si₁₂O₃₇](H₂O,O,OH)₁₇, is monoclinic, with cell parameters a 16.47, b 5.303, c 24.39 Å, ß 93.5°, Z = 2. It was collected on the dumps of the Umbozero mine, Mount Alluaiv, Lovozero massif, Kola Peninsula, Russia. It is associated with albite, elpidite, epididymite, quartz, natrolite, pyrite, galena, sphalerite and bitumen. Caryochroite is the product of the supergene alteration of an unidentified Fe²⁺-rich protophase; it forms centimetric crusts. Physical properties: submicrometric {001} lamellae, [010] elongate; opaque; hazel-brown color; pale brownish yellow streak; dull to waxy luster; hardness, 2 good {001} cleavage; D_meas 2.990 g cm^–3; biaxial (–), <1.700, ß 1.745, 1.775, 2V_meas 75°; pleochroism: X = Y (dark brown) > Z (brown). The name refers to the color. Chemical data from electron microprobe, wet-chemical analysis for Fe and thermal analysis (9.17 wt% loss at 800°C); Mössbauer spectroscopy shows major Fe³⁺ and minor Fe²⁺; the empirical formula is (Na_1.19Sr_0.62Ca_0.41Mn_0.35K_0.26)_2.83 (Fe_7.98 ³⁺Mg_1.15Mn_0.49Fe_0.38 ²⁺)_10.00 (Ti_1.87Fe_0.13 ³⁺)_2.00 (Si_11.74Al_0.26)_12.00 O_54.10H_20.40. The spacing (Å) and intensity (%) of the strongest six lines of the X-ray powder-diffraction pattern are: 14.1(20), 13.3(30), 12.1(100), 4.38(10), 2.692(12), and 2.631(13). The cell parameters, X-ray powder-diffraction pattern, chemical composition and infrared spectrum suggest that caryochroite is the second heterophyllosilicate based on a nafertisite-type HOH layer. We evaluate the role of caryochroite and associated titano- and zirconosilicates as catalysts of the in situ formation of bitumen.

Keywords: caryochroite, new mineral species, heterophyllosilicates, nafertisite, titanosilicate, Kola Peninsula, Lovozero massif, bitumen catalysis.