Cookeite with a perfect regular structure, formed by bauxite alteration
1975; Mineralogical Society of America; Volume: 60; Linguagem: Inglês
ISSN
1945-3027
AutoresZoya V. Vrublevskaja, I.S. Delitsin, B. B. Zvyagin, С. В. Соболева,
Tópico(s)Clay minerals and soil interactions
ResumoA di,trioctahedral Li-chtorite cookeite (Lio.?Alr.r )r.s(Alr.rFe;.tnFe3.+or), ,rISi, ,rAlo u2],.oO,o . (OH)tu, with an exceptionally perfect crystal structure has been found in bauxite of Djalair (Middle Asia). High-voltage diffraction (oblique-texture) patterns were used for its structural identification. It was established that it is a oneJayer triclinic polytype lo'uo'rlraraloLoll ..w i t h s y m m e t r y C i a n d u n i t c e l l : a 5 . 1 4 , b : 8 . 9 0 , c : l 4 . l 5 A , a : 9 0 o 3 3 ' , A : 9 6 1 2 ' , 1 = 90'. The small deviation ofa from 90o results in very peculiar features ofthe diffraction patterns, giving the false impression of a monoclinic lattice but with two non-selfconsistent Bvalues. The formation of the cookeite investigated is the final result of a peculiar transformation of bauxite rock following an intermediate stage of formation of a two-layer monoclinic pyrophyllite polytype.
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