Growth sectors

Figure 6.3. Expected difference in the features of growth banding in respective growth sectors depending on the order of morphological importance (MI, > MI >Ml3).A, B, and C indicate growth sectors corresponding to respective faces and the features to be observed in growth banding. The distribution of dislocations is not indicated.

Growth banding seen in different growth sectors will have different features depending on the order of morphological importance. This is due to environmental conditions. 

Figure 6.3 illustrates schematically features seen in the growth banding patterns in respective growth sectors, in relation to the order of morphological importance of the crystal faces. A rough interface disappears as growth proceeds, but the... 

Figure 6.4. Forms of growth sector boundaries depending on the relation between and Rj.

Some crystals exhibit a texture called a center-cross pattern, the origin of which was, at one time, a subject of controversy, as to whether the origin was by growth or by plastic deformation. The center-cross pattern is schematically illustrated in Fig. 9.12 it corresponds to a texture shown by the growth sectors of two coexisting crystal faces, lll and 100. This pattern indicates that the arms of the cross correspond to the growth sectors of 100, which disappear at the later stage of... 

Figure 9.12. Growth sector showing a center-cross pattern formed by the growth of smooth 111 and rough 100 interfaces.

This experiment demonstrates that a distinction between the r and z faces based on the size difference becomes impossible. Also, the growth sector of the z face takes on a violet color. In an isotropic environment, the violet coloring appears selectively in the r growth sectors, and the z growth sectors are colorless. This experiment also demonstrates that the partitioning of impurity Fe is affected by the growth rate. 

In amethyst crystals showing Brewster fringes, a pattern such as that shown in Fig. 10.14 is observed in the growth sectors of or on the surface of r faces, and not in... 

The portions corresponding to the growth sectors are formed by filling up the interstices of the earlier-formed skeleton. The growth in this stage is single phase and slow. 

The above process is well recorded in element partitioning in trapiche ruby. Figure 13.4 shows the summarized results of micro-area XRF (X-ray fluorescence spectroscopic analysis) [3]. The partitioning of Cr, Fe, and Ti in corundum in the core portion, the dendritic portion, and the growth sectors is indicated. The following points should be noted. 

The content of Cr in corundum in the dendritic portion is lower than that in both the core portion and the growth sectors, and is nearly constant from the root to the tip of the dendrite. 

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