Study of the arangasite stability by methods of X-ray and thermal analyses

Zayakina N. V., Emelyanova N. N.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2015. V. 144. N 4. P. 109-115

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Language: Russian

Abstract

Arangasite, a rare hydrated sulfate-phosphate aluminum fluoride, has been studied by X-ray diffraction (XRD) and differential thermal analysis (DTA). It has been established that the mineral may contain different amounts of water depending on the environment humidity. It is proposed to write down the formula of the mineral as Al₂(PO₄)(SO₄)(SO₄)F · (7.5—9)H₂O. The XRD pattern of the mineral after some lost of water differs significantly from the initial arangasite pattern. After losing 1—1.5 water molecules the mineral remains capable for rehydration with the complete restoring of the structure. The paper displays data on loss of water while the heating of arangasite, its thermogram, XRD patterns of samples with different water content.

Key words: arangasite, X-ray diffraction and differential thermal analysis, rehydration.