Characters of Plastic Deformation on Diamonds from Hunan Province, China

The studied diamonds come from the Yuanjiang River in Hunan Province, China. The diamonds were etched strongly, the etched lines and etched dislocation channels can be seen on the surface of diamond. The most commons are two sets lines, up to four sets occasionally. The line parallels each other in the same set, but across between two sets. Rows etched dislocation channels that represent zones of weakness in the crystal structure distribute along main deformed faces. Studies on the chosen polished slab specimens for micro-characters by gem microscope and polarizering microscope, cathodoluminescence (CL) show that the parallel extinctions caused by the main plastic deformation planes are clear under crossed polarizers, with two sets of parallel extinctions intersecting, three sets forming ring, four sets forming a strain phantom. The brown bands are closely related to the parallel extinctions; the brown bands are surely accompanied by the parallel extinctions, but the parallel extinctions do not guarantee to be accompanied by the brown bands. TEM shows both screw and knife dislocation can be seen and dislocation tangle is very clear; the dislocation density is uneven distribution: the density in tangle belt is clearly higher than that in the zone between two belts. The plastic deformation occurred after the growth stage of diamond.