<Original Papers>Hematitization of α-type Limonite by Thermal Dehydration

The crystallization process of poorly crystallized ferric oxide formed by the dehydration of three α-type limonites obtained from different localities was studied by means of X-ray powder method. The results are as follows : 1) α-type limonite changes into a mixture of poorly crystallized hematite and amorphous ferric oxide by its thermal decomposition in the temperature range 390-405℃. These two heated products arise from crystalline goethite and amorphous ferric oxide hydrate contained respectively in original limonite. 2) Variations in the degree of crystallization of hematite changed from limonite by heating depend on the difference in the crystallinity of original goethite. 3) At low temperature from 350 to 550℃, the transformation of amorphous ferric oxide into hematite crystallite is predominent, compared with the growth of hematite crystallite. 4) The hematite crystallite formed at low temperature has a tendency of the two dimensional lattice up to about 750℃, and then grows gradually with rising temperature. 5) The crystallization process of poorly crystallized hematite and amorphous ferric oxide formed by thermal dehydration of α-type limonite may be shown as follows : [numerical formula