Optical symmetry, also known as “3D Symmetry” is the direct internal interaction of all the different facets of a diamond. Optical Symmetry directly correlates to the overall craftsmanship of a diamond and the level of precision to which it was cut. Where as the Symmetry grade listed on Lab Reports is the grading of external physical symmetry characteristics of a diamond such as the external meet points of facets, Optical Symmetry correlates to how the facets of a diamond align with each other internally and how light is reflected from the alignment and interaction of these different facets. Optical symmetry therefore measures the consistency of angles and configuration of facets by effectively measuring the equality of light return.
Optical Symmetry is measured by direct assessment, meaning that it is assessed based on the way each diamond actually performs and reflects light.. Furthermore, Optical Symmetry is not noted or graded on Lab Reports BUT can be observed using various reflector technologies the most well known of which is the Hearts & Arrows Scope. The purpose of this scope is to reveal the patterns of the diamond’s light return in relationship to its proportions, viewpoints and angles. The more even the pattern, the better the Optical Symmetry. All light returned (reflected out of the diamond) at the same angles is characterized by the same color in the image. For example; all red areas represent light being returned within a consistent angle range.
When a diamond has excellent optical symmetry such as the Canera Ideal Hearts Diamond and is polished to specific proportions, a kaleidoscopic effect will be revealed when viewing the diamond through a Hearts & Arrows scope. When viewing the diamond through the pavilion, eight equal and symmetric hearts pattern will become apparent. When viewing the diamond top down through a hearts and arrows viewer, eight symmetric arrows will be visible.
It is important to note that all diamonds can potentially have a high level of optical symmetry including fancy shaped diamonds. The Canera European Round diamond for example is not polished for hearts and arrows proportions but exhibits exemplary optical symmetry. The precise interaction of the various facets in the CER can be clearly seen through its various scope images. Fancy shaped diamonds can also potentially have a high level of optical symmetry. One such specimen of a fancy shaped diamond having excellent optical symmetry is the Canera Antique Cushion diamond.