Feature Gems & Gemology, Summer 1992. Vol. 28, Issue 2

An Update on Sumitomo Gem-Quality Synthetic Diamonds

Examination of two large (5.06 and 5.09 ct) tabular pieces of Sumitomo synthetic diamond revealed that they were cut from single crystals of predominantly cubic {100} and octahedral {111} morphologies, respectively. These two crystal forms exhibit different patterns of color zoning, internal graining, anomalous birefringence ("strain”), and luminescence. Such differences suggest that both crystal morphology and size can greatly affect the properties observed in a synthetic diamond.