The Nature of Garnierites—III Thermal Transformations

Pham Thi Hang and G. W. Brindley
Department of Geosciences, and Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A.

Abstract: Serpentine- and talc-like garnierites described in Parts I and II were heated at various temperatures up to about 1000°C and after each treatment were cooled and examined by X-ray powder diffraction. The serpentine-like garnierites at about 550°C the temperature at which rapid dehydroxylation begins, formed a highly disordered phase. When the NiO content was low (approximately < 20 wt%), the disordered phase transformed directly to an olivine phase around 800°C but when the NiO content was higher, various transitional phases were formed before an olivine phase appeared around 1000°C A sepiolite-like phase was obtained with one sample around 800°C and several samples showed face-centered cubic modifications between 900 and 1000°C.

The talc-like garnierites with low NiO content formed an enstatite phase around 800°C directly following the dehydroxylation reaction, but with high NiO contents an olivine phase became increasingly prominent between 850 and 1000°C. Identification of the mixed crystallizations possibly existing in the initial minerals is scarcely feasible on the basis of the products formed up to 1000°C.

Clays and Clay Minerals; February 1973 v. 21; no. 1; p. 51-57; DOI: 10.1346/CCMN.1973.0210108
© 1973, The Clay Minerals Society
Clay Minerals Society (www.clays.org)