Artificial Alteration of Biotite into a 14 Å Layer Silicate with Hydroxy-Aluminium Interlayers

K. Nagasawa*, G. Brown and A. C. D. Newman
Pedology Department, Rothamsted Experimental Station, Harpenden, Hertfordshire, England
* Permanent address: Department of Earth Sciences, Nagoya University, Chikusa, Nagoya, Japan.

Abstract: Biotite was altered by boiling in 0·2 M AlCl3 solution, and the products were examined by X-ray powder and single-crystal diffraction, chemical analysis and thermogravimetry. The altered material is a 14 Å clay mineral with hydroxy-Al interlayers. It has a stacking sequence characteristic of vermiculite and its silicate layers are similar in chemical composition to trioctahedral vermiculite. The results of extracting the interlayer material with sodium citrate solution, X-ray examinations after heating and thermogravimetry show that the interlayer material is composed of Al associated with OH and H2O. The chemistry and kinetics of the alteration reaction and the orientational between the altered and original biotites are also discussed.

Clays and Clay Minerals; June 1974 v. 22; no. 3; p. 241-252; DOI: 10.1346/CCMN.1974.0220306
© 1974, The Clay Minerals Society
Clay Minerals Society (www.clays.org)