1953 Volume 17 Issue 12 Pages 628-632
The sets of figures produced by zinc crystals as etched under various conditions always contain one kind of light figure of the hexagonal symmetry corresponding to {0001} planes and may be classified into two groups in view of the fact that the six-arrows usually appearing in the {0001} light figure point either to {10\bar10} poles (the first group) or to {11\bar20} poles (the second group). The first group of light figures may further be divided into three sub-groups: IA, IB and IC. The IA group contains the {0001} light figure and two kinds of light figures of the digonal symmetry corresponding to {10\bar10} and {11\bar20} planes, the IB group consists of {0001} and {10\bar10} light figures, and the IC group consists usually of {0001}, {10\bar10} and {11\bar20} light figures and some times contains also light figure of the digonal symmetry of rotatory reflection corresponding to {10\bar11} planes. On the other hand, the second group contains {0001}, {101\bar0}, {112\bar0}, {10\bar12}, {10\bar11}, {11\bar26} and {41\bar50} light figures. It is also shown from the form of observed light figures that {0001} and {10\bar1l} planes are developed by etching which produces the IA and IB groups of light figures, and {0001}, {10\bar10}, {11\bar20} and {1\bar011} planes are developed by etching which produces the IC group, while {0001}, {10\bar10}, {11\bar20}, {10\bar12}, {10\bar11}, {11\bar2l} (l≥6) and {41\bar50} planes are developed by etching which produces the second group.