High-quality yellow, orange-yellow, and yellow-orange laboratory-created type Ib diamond crystals up to 3.5 ct are being produced commercially by the Gemesis Corp. of Sarasota, Florida. In some samples, color zoning (yellow and narrower colorless zones) and a weak UV fluorescence pattern (a small green cross-shaped zone combined with an overall weak orange luminescence) provide means of identification; when present, metallic inclusions also indicate laboratory growth. Some samples lack these diagnostic visual features, but all of these Gemesis synthetic diamonds can be identified by advanced instrumentation such as the De Beers DiamondView luminescence imaging system and EDXRF chemical analysis.
