Extremely fluorine-rich fluoborite from fumarolic exhalations of the Tolbachik volcano (Kamchatka)

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Marco E. Ciriotti
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Iscritto il: ven 25 giu, 2004 11:31
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Extremely fluorine-rich fluoborite from fumarolic exhalations of the Tolbachik volcano (Kamchatka)

Messaggio da Marco E. Ciriotti » lun 05 lug, 2021 11:03

Referenza:
▪ Bulakh, M.O., Pekov, I.V., Chukanov, N.V., Yapaskurt, V.O., Koshlyakova, N.N., Britvin, S.N., Sidorov, E.G. (2021): Extremely fluorine-rich fluoborite from fumarolic exhalations of the Tolbachik volcano (Kamchatka). Zapiski RMO, 150(2), 42-56.

Abstract
Fluoborite extremely close to the fluorine end-member of the fluoborite Mg3[BO3]F3–hydroxylborite Mg3[BO3](ОН)3 series, was found in exhalations of the Arsenatnaya fumarole (Tolbachik volcano, Kamchatka, Russia). The amount of the Mg3[BO3](ОН)3 component in it does not exceed 1 mol %. This borate is associated with halite, sylvite, langbeinite-group and aphthitalite-group sulfates, anhydrite, krasheninnikovite, sanidine, fluorophlogopite, hematite, tenorite, chubarovite, alluaudite-group arsenates, lammerite and urusovite. Fluoborite forms here fine acicular or hair-like crystals up to 5 mm long assembled in radial, near-parallel or chaotic open-work aggregates up to 10 cm across. Its chemical composition determined by the electron microprobe is: Mg 38.71, B 5.90, O 25.52, F 30.83, total 100.96 wt %; the empirical formula is: Mg2.97B1.02O2.98F3.03. The unit-cell parameters calculated from the powder X-ray diffraction pattern are: a = 8.808(4), c = 3.098(2) Å, V = = 208.1(3) Å3. The IR and Raman spectra of borates of the fluoborite–hydroxylborite series are given and discussed. Fluoborite in the Arsenatnaya fumarole crystallized at a temperature not lower than 450 °C. The fumarolic genetic type is novel for this borate.
Marco E. Ciriotti

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