Avdoninite: new data, the crystal structure and refined formula К2Сu5С18(ОН)4·2Н2O

Pekov I. V., Krivovichev S. V., Chukanov N. V., Yapaskurt V. O., Sidorov E. G.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 3. P. 55-69

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Language: Russian


New finds of avdoninite in the deposits of active fumaroles at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia, are reported. The crystal structure of the mineral, unknown before, is studied, its space group and unit cell parameters are determined at the first time, its formula is refined as K2Cu5Cl8(OH)4 · 2H2O and its powder X-ray diffraction pattern is correctly indiced. Avdoninite is monoclinic, P21/c, a = 11.592(2), b = 6.5509(11), c = 11.745(2) Å, β = 91.104(6)°, V = 891.8(3) Å3 and Z = 2. The crystal structure is solved from single-crystal X-ray diffraction data and converged to R1 [F > 4 σ (F)] = 0.063. It is based upon layers consisting of copper-oxochloride complexes [Cu5Cl8(OH)4]2- coplanar to the (100) plane. The K+ cations and H2O molecules are located in the interlayer.

Key words: avdoninite, copper oxochloride, crystal structure, fumaroles, Tolbachik volcano, Kamchatka.