MECHANISM OF CRYSTAL GROWTH, ETCHING AND TWIN FORMATION OF HEMATITE

Abstract

The surface structures of hematite crystals from nine localities are observed with an ordinary reflecting and a phase contrast microscope, and the step heights of growth layers as well as the other surface features are measured precisely with multiple-beam interferometric method and the method of fringes of equal chromatic order. On the basis of these observations and measurements, mechanism of crystal growth, natural etching, twin formation and movement of screw dislocations after the cessation of growth and the possibility of polytypism are discussed in this paper. Physical and chemical conditions under which hematite crystals have grown are also discussed on the basis of characteristics of growth and etch patterns.