Montmorillonite Pseudomorphs after Amphibole from Melbourne, Australia

W. F. Cole and C. J. Lancucki
Commonwealth Scientific and Industrial Research Organization, Melbourne, Australia

Abstract: Well developed smectite “crystals” up to 10 mm long, which probably are pseudomorphic after titaniferous hornblende phenocrysts, are present in a weathered dike in a Melbourne clay pit. The pseudomorphs contain 77 per cent of montmorillonite as determined by X-ray powder diffraction, differential thermal analysis, thermo-gravimetric and chemical analysis. The pseudo-hexagonal shape of the pseuodomorphs probably reflects the original crystal habit of the hornblende. The mechanism of alteration of an amphibole to a smectite is discussed.

Clays and Clay Minerals; April 1976 v. 24; no. 2; p. 79-83; DOI: 10.1346/CCMN.1976.0240205
© 1976, The Clay Minerals Society
Clay Minerals Society (www.clays.org)