Cleavage System in Pink Diamond
A 0.29 ct natural Fancy Intense purplish pink diamond with a microscopically interesting geometric feature (figure 1) was recently examined at GIA’s Carlsbad laboratory. A network of planar cracks, oriented in three octahedral directions, was observed at the surface of a pavilion facet (figure 2). These linear cleavage cracks were caused by localized strain on an octahedral plane.
The octahedral plane in diamond has the weakest atomic bonding, which means that when a diamond is strained, this is the direction that will be most affected. This stone offers the perfect example of strain products in pink diamond. The purplish pink color results from plastic deformation along octahedral planes. Also present along the octahedral plane is a zone where the strain was so great that it was relieved by cracking, creating the cleavage network seen in figures 2 and 3.
The cleavage network in this diamond is the most aesthetic one encountered by the author to date due to its finely textured geometric pattern. Interestingly, the clue to the planar cleavage network lies in the bodycolor of the stone, which indicates significant strain. This high-order strain is easily revealed between crossed polars. If a cleavage network is present in a diamond such as this, it may have a strain-induced bodycolor as well.
