New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XIV. Badalovite, NaNaMg(MgFe3+)(AsO4)3, a member of the alluaudite group

Igor V. Pekov, Natalia N. Koshlyakova, Atali A. Agakhanov, Natalia V. Zubkova, Dmitry I. Belakovskiy, Marina F. Vigasina, Anna G. Turchkova, Evgeny G. Sidorov, Dmitry Yu. Pushcharovsky
2020 Mineralogical magazine  
The new alluaudite-group mineral badalovite 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 hematite, tenorite, cassiterite, johillerite, nickenichite, calciojohillerite, bradaczekite, metathénardite, aphthitalite, langbeinite, calciolangbeinite, sanidine, fluorophlogopite, fluoborite, tilasite, anhydrite, pseudobrookite, sylvite, halite, lammerite,
more » ... alite, lammerite, urusovite, ericlaxmanite, arsmirandite, svabite, krasheninnikovite, euchlorine, wulffite, and alumoklyuchevskite. Badalovite forms oblique-angled prismatic crystals up to 1 × 1 × 5 mm typically combined in groups or crusts up to several hundred cm 2 in area. The mineral is transparent, green, grey, yellow or colourless, with vitreous lustre. It is brittle, the Mohs hardness is 3½. Cleavage was not observed, the fracture is uneven. D calc is 4.02 g cm -3 . Badalovite is optically biaxial (-), α = 1.753(3), β = 1.757(3), γ = 1.758(3), 2V meas. = 50(10)º. Chemical composition (wt.%, electron-microprobe; holotype) is: Na 2 O 9.23, K 2 O 0.19, CaO 2.04, MgO 13.78, MnO 0.31, CuO 2 0.12, ZnO 0.24, Al 2 O 3 0.06, Fe 2 O 3 12.77, TiO 2 0.01, SiO 2 0.06, P 2 O 5 0.33, V 2 O 5 0.05, As 2 O 5 61.51, SO 3 0.02, total 100.72. The empirical formula based on 12 O apfu is The simplified formula is Na 2 Mg 2 Fe 3+ (AsO 4 ) 3 . Badalovite is monoclinic, C2/c, a = 11.9034(3), b = 12.7832(2), c = 6.66340(16) Å, β = 112.523(3)º, V = 936.59(4) Å 3 and Z = 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 6.The crystal structure was solved from single-crystal XRD data, R = 2.49%. Badalovite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is A(1) (2) (Mg 0.5 Fe 3+ 0.5 ) 2 (AsO 4 ) 3 (□vacancy) and the end-member formula is NaNaMg(MgFe 3+ )(AsO 4 ) 3 . The mineral is named in honour of the outstanding mineralogist and geochemist Stepan Tigranovich Badalov .
doi:10.1180/mgm.2020.43 fatcat:xn2ztgesdvhxteo3qmnga3b6be