New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IX. Arsenatrotitanite, NaTiO(AsO4). (4th July 2018)

• Record Type: Journal Article
• Authors: Pekov, Igor V.; Zubkova, Natalia V.; Agakhanov, Atali A.; Belakovskiy, Dmitry I.; Vigasina, Marina F.; Yapaskurt, Vasiliy O.; Sidorov, Evgeny G.; Britvin, Sergey N.; Pushcharovsky, Dmitry Y.
• Is Part Of: Mineralogical magazine. Volume 83:Number 3(2019)
• Page Start: 453
• Page End: 458
• Publication Date: 2018-07-04
• Subjects: arsenatrotitanite, -- new mineral, -- sodium titanium arsenate, -- durangite group, -- titanite group, -- crystal structure, -- fumarole sublimate, -- Tolbachik volcano, -- Kamchatka; Mineralogy -- Periodicals; Mineralogy -- Great Britain -- Periodicals; 549.05
• DOI: 10.1180/mgm.2018.134
• Languages: English
• ISSNs: 0026-461X

Abstract

Abstract: The new durangite-group mineral arsenatrotitanite, ideally NaTiO(AsO4 ), was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with orthoclase, tenorite, hematite, johillerite, bradaczekite, badalovite, calciojohillerite, arsmirandite, tilasite, svabite, cassiterite, pseudobrookite, rutile, sylvite, halite, aphthitalite, langbeinite and anhydrite. Arsenatrotitanite occurs as prismatic, tabular, lamellar or acicular crystals up to 0.3 mm × 0.8 mm × 2 mm. They are separated or combined in open-work aggregates up to 2 mm across or interrupted crusts up to 2 mm × 5 mm in area and up to 0.3 mm thick. Arsenatrotitanite is transparent, brownish red to pale pinkish-reddish or almost colourless, with vitreous lustre. It is brittle and the Mohs' hardness is ~5½. Cleavage is perfect on {110} and the fracture is stepped. D calc is 3.950 g cm –3 . Arsenatrotitanite is optically biaxial (+), α = 1.825(5), β = 1.847(6), γ = 1.896(6) (589 nm) and 2Vmeas. = 70(5)°. Chemical composition (wt.%, electron-microprobe) is: Na2 O 12.26, CaO 3.10, Al2 O3 4.39, Fe2 O3 9.57, TiO2 17.11, SnO2 1.03, As2 O5 50.17, F 3.29, O = F –2.39, total 99.53. The empirical formula based on 5 (O + F) apfu is (Na0.91 Ca0.13 )Σ1.04 (Ti0.49 Fe 3+ 0.27 Al0.20 Sn0.02 )Σ0.98 (As1.00 O4.00 )(O0.60 F0.40 ). Arsenatrotitanite is monoclinic, C 2/ c, a = 6.6979(3), b = 8.7630(3), c = 7.1976(3) Å, β = 114.805(5)°, V = 383.48(3) Å 3 and Z = 4. The strongest reflections of the powder X-ray diffraction (XRD) pattern [ d, Å( I )( hkl )] are: 4.845(89)( $\bar{1} {11}}$ ), 3.631(36)(021), 3.431(48)(111), 3.300(100)( $\bar{1} {12}}$ ), 3.036(100)(200), 2.627(91)(130) and 2.615(57)(022). The crystal structure was solved from single-crystal XRD data with R = 1.76%. Arsenatrotitanite belongs to the titanite/durangite structure type. It is named as an arsenat e of sodium ( natr ium in Latin) and titani um isostructural with titanite .