Cancrinite specimens from Ontario were studied. Chemical and thermogravimetric analyses were made. Non-Bragg reflections were observed in x-ray photographs. These reflections have the same symmetry as the main lattice reflections, but the intensities, abundance and the relative positions of them with respect to the main lattice reflections are different from one specimen to another. In the heated specimens, the superstructure reflections decrease in intensities, shift in position and are streaked in a direction parallel to the a*-axis on the a* c* reciprocal lattice plane. Phase changes in the heated cancrinites show that the sodalite group of minerals occur as transitional phases in the cancrinite break down reactions. It is shown that the non-Bragg reflections are very similar to the main lattice reflections. There is a probable relation between the non-Bragg reflections in cancrinite and the sodalite group of minerals. / Thesis / Master of Science (MSc)