Kationenaustausch von Peristeriten mit Beobachtungen an Pulver- und Einkristallaufnahmen

Plagioclase crystals with compositions in the peristerite range have been studied by Weissenberg method. Many reflections with small Bragg angles are found to show three distinct peaks. The middle peak vanishes with increasing values of Bragg angles. On the contrary, the first fifty lines of the corresponding powder photographs could be indexed on the basis of only one lattice. All these observations can be explained with the help of a satellite theory, assuming the existence of a coherently scattering, modulated lattice.