Abstract
Transmission electron microscope images of the zeolite ferrierite, prepared by ultramicrotomy as cross sections of the main-channel axis, revealed several types of crystallographic defects. Both shear faults and sigma transformations occur in the vug-filling bundles of ferrierite near Kamloops Lake, British Columbia. Sigma contraction {110} planes occur as discrete domains several unit cells thick. Shear faults involving displacements of (a ± b)/2 on {110} planes occur in lesser amounts. In addition, mordenite occurs in the Kamloops Lake sample, underscoring the frequent association of these zeolites, their crystal chemical and structural affinities, and the importance of TEM-scale observations in petrologic studies of fine-scale intergrowths of zeolites.