Experimental constraints on illite crystal morphology
Abstract:Observations of natural minerals and experimental run products show that I-S (illitesmectite mixed-layer minerals) with a high illite content as well as pure mica-illite crystallites can have a lath shape (aspect ratio >3). This shape is common to the I-S minerals under a variety of conditions of formation. The experiments presented indicate that the occurrence of lath-shaped micaillite is due to a slow growth rate from supersaturated solutions. This lath-shaped crystallite is metastable as the ultimate stable shape is hexagonal. A longer period of crystal growth will replace the mica-illite laths with crystallites of a hexagonal form. Thus the presence of lath-shaped micaillite indicates the existence of a metastable crystal form for this mineral.
Document Type: Research Article
Affiliations: 1: Forschungszentrum Karlsruhe, Institut fu ¨r Nukleare Entsorgungstechnik, PO Box 3640, D-76021 Karlsruhe, Germany 2: Laboratoire de Ge´ologie, CNRS URA 1316, Ecole Normale Supe´rieure, 24 rue Lhomond, F-75231 Paris,France
Publication date: 2000-06-01