Abstract
Surface structures 011 the basal planes and other faces of hematite crystals from many localities have been observed with both metallurgical and phase contrast microscopes. It is concluded that the growth lakes place mainly by two-dimensional spreading of growth layers parallel to (0001), and that the other faces are formed mainly by the edges of these layers, although growth layers parallel to these other faces can develop when they become large.
It is also concluded that at an early stage, two-dimensional nucleation is responsible for the major growth, but later growth layers may originate from deformed portions of the surface, or from a group of dislocations, both of which are due to stresses applied to the crystal. Most of the thick growth layers are formed by the coalescence of thinner layers, but some originate independently. Only at the later stage, or under very low supersaturation, can typical spiral patterns be formed. From the characteristics of the growth patterns on crystals from different localities, a sequence is arranged, showing decrease in supersaturation conditions.
