Feature Gems & Gemology, Winter 1986, Vol. 22, No. 4

The Gemological Properties of the Sumitomo Gem-Quality Synthetic Yellow Diamonds

The distinctive gemological properties of the gem-quality synthetic yellow diamonds grown by Sumitomo Electric Industries are described. These synthetic diamonds, produced on a commercial basis, are grown as deep yellow single crystals in sizes up to 2 ct. The material is currently marketed for industrial applications only, in pieces up to about 0.40 ct. The synthetic diamonds can be distinguished by their ultraviolet fluorescence (inert to long-wave; greenish yellow or yellow to short-wave); their unusual graining, veining, and color zonation under magnification; and the absence of distinct absorption bands in their spectra.