THERMAL TRANSFORMATION OF MUSCOVITE IN MOLTEN KCl

抄録

Muscovite heated in molten KCl at 900°C to 1, 100°C was studied by means of X-ray analysis, optical and electron microscopy. The mineral newly formed by this treatment was identified to be kaliophilite from X-ray powder data. Crystals of the kaliophilite are acicular in form and are aligned in two directions at 120° on muscovite with the topotaxial relations: pseudo b_mus//c_kalio, pseudo a_mus//a_kalio and [001]_mus//[1^-100]_kalio. These relations suggest that oxygen layers of muscovite, which are perpendicular to the tetrahedral sheet and include pseudo a-axes are inherited to the structure of synthetic kaliophilite, while the oxygen plane (001) in muscovite is not. The kaliophilite gives a diffraction pattern consisting alternately of rows of spots and lines perpendicular to c^*, suggesting that the synthetic kaliophilite has statistical displacements in (100). The structure with ordered displacements will be that of natural kaliophilite.