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Structure refinement of astrophyllite |
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| Authors: | Ma Zhesheng LI Guowu Shi Nicheng ZHOU Huyun YE Danian DYUPUSHCHAROVSKY |
| Institution: | 1. China University of Geosciences, Beijing 100083, China; 2. Southwest Institute of Technology, Mianyang 621002, China 3. China University of Geosciences, Beijing 100083, China 4. Institute of Geology, Chinese Academy of Sciences, Beijing100029, China 5. Department of Geology, Moscow State University, Moscow 119899, Russia |
| Abstract: | The crystal structure of astrophyllite K2Na(Fe, Mn, Mg,□)7Ti2(Si4O12)2|O3](OH, F)4 has been refined. The dimensions of the triclinic unit cell are: a = 0.5359(2) nm,b = 1.1614(4) nm, c = 1.1861(4) nm, α= 113.16(2)°, β= 103.04(2)°,γ= 94.56(2)°,V = 0.6495(5) nm3, Z= 1, space group P1, R=0.057 for 5308 reflections |Fo|>3σ|Fo|. According to structural and compositional differences the monoclinic astrophyllite K2NaNa(Fe, Mn)4Mg2Ti2Si4O12]2(OH)4(OH, F)2 and astrophyllite should be considered as two different mineral species. Astrophyllite, monoclinic astrophyllite, bafertisite and lamprophyllite contain heteropolyhedral sheets which topologically are related with Si, O sheets of mica where one or several SiO4 tetrahedra are replaced by TiO n polyhedra. Therefore this heterophyllotitanosilicate series represents a kind of functional substitution in inorganic crystals. |
| Keywords: | astrophyllite crystal structure functional substitution |
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