Affiliation:
1. Lomonosov Moscow State University, Faculty of Geology
2. Fersman Mineralogical Museum of the Russian Academy of Sciences
3. Institute of Volcanology and Seismology, Far Eastern Branch of Russian Academy of Sciences
Abstract
A new, unusual Fe-free and As5+-enriched variety of chladniite, a rare phosphate of the fillowite group was found in exhalations of the active Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. It belongs to the high-temperature (500–750°С) paragenesis with calciojohillerite, fluorapatite, metathénardite, diopside, enstatite, forsterite and hematite. This genetic type is novel for fillowite-group minerals. The crystal structure of Tolbachik chladniite is solved, R1 = 4.32%. It is trigonal, R–3, a = 14.9831(2), c = 42.8050(7) Å, V = 8322.1(3) Å3. The structural formula is: M13(Na0.56\(\square \)0.44)\(_{2}^{{M21}}\)(Na0.81Ca0.19)\(_{2}^{{M31}}\) (Na0.97\(\square \)0.03)\(_{6}^{{M12}}\)(Ca0.64Na0.36)\(_{6}^{{M1}}\)MnM2(Mg0.54Ca0.46)M3–9Mg\(_{{30}}^{{M10}}\)(Mg0.94Ca0.06)\(_{6}^{{M11}}\)Mg6(P33.53As2.47)O144 (Z = 3). The crystal chemical features of chladniite and their correlation with mode of occurrence are discussed for all chladniite findings known in meteorites and terrestrial objects of different genetic types.
Publisher
The Russian Academy of Sciences
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