High-temperature behavior of lamprophyllite and barytolamprophyllite

Zhitova E. S., Panikorovskii T. L., Yakovenchuk V. N., Krzhizhanovskaya M. G.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 3. P. 82-94


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Language: Russian


According to the high-temperature X-ray powder diffraction data, lamprophyllite and barytolamprophylhte are stable up to 925 and 850 °C, respectively. The temperature of decomposition was defined for barytolamprophyllite by DSC and TGA methods as 897 °C. Analysis of the X-ray diffraction pattern during the heating has not detected any significant changes, implying the absence of phase transitions. Behavior of lamprophyllite and barytolamprophylhte at high-temperature is strongly anisotropic, thermal expansion coefficients (×106) along crystallographic axes at T = 200 °C are as following: aa = 12.6(6), ab = 7.7(1), ac = 4.4(2) °C–1 for lamprophyllite, and aa = 11.8(5), ab = 5.7(1), ac = 3.4(3) °C–1 for barytolamprophylhte. At T = 600 °C these values are aa = 15.2(5), ab = 7.7(1), ac = 2.2(2) °C–1 for lamprophyllite, and aa = 12.3(7), ab = 5.7(1), ac = –3.8(4) °C–1 for barytolamprophylhte. The contraction along the axis ñ was observed for barytolamprophyllite, but did not for lamprophyllite; it is caused by thermal oxidation of iron.

Key words: lamprophyllite, barytolamprophylhte, high-temperature X-ray diffraction.