The authors recently examined a 0.57 ct J-color round brilliant natural diamond with an SI1 clarity grade based on a rare formation of hair-like loops (see above). This inclusion, which resembled the “horsetail” fibrous inclusions in demantoid garnet, was best showcased when viewed through the pavilion under a microscope. These loops seemed to defy the monocrystalline structure of diamond, in which angular and straight-edged internal features are typical and distinctly curved structural features are rare. Diamonds often undergo plastic deformation in the earth, and linear surface and internal graining are visible manifestations of this process. During diamond growth, both plastic deformation and the precipitation of microscopic to submicroscopic foreign matter on growing surfaces can increase dislocation density, and the presence of one dislocation may lead to the development of more (Spring 2007 Lab Notes, pp. 48–49).
Nilay Patel is a diamond grader specialist, Jaydip Dhameliya is a quality specialist, and Raju Jain is a training specialist, at GIA in Surat, India.
The authors recently examined a 0.57 ct J-color round brilliant natural diamond with an SI1 clarity grade based on a rare formation of hair-like loops (see above). This inclusion, which resembled the “horsetail” fibrous inclusions in demantoid garnet, was best showcased when viewed through the pavilion under a microscope. These loops seemed to defy the monocrystalline structure of diamond, in which angular and straight-edged internal features are typical and distinctly curved structural features are rare. Diamonds often undergo plastic deformation in the earth, and linear surface and internal graining are visible manifestations of this process. During diamond growth, both plastic deformation and the precipitation of microscopic to submicroscopic foreign matter on growing surfaces can increase dislocation density, and the presence of one dislocation may lead to the development of more (Spring 2007 Lab Notes, pp. 48–49).
Nilay Patel is a diamond grader specialist, Jaydip Dhameliya is a quality specialist, and Raju Jain is a training specialist, at GIA in Surat, India.
