gems, synthetic diamond

Gem-quality synthetic diamond crystals weighing up to 11 carats have been grown experimentally in limited quantities at the De Beers Diamond Research Laboratory since the 1970s, though they are not commercially available. Examination of 14 synthetic diamonds in shades of brownish yellow, yellow, and greenish yellow reveals distinctive gemological features, including uneven color distribution, geometric graining patterns, metallic inclusions, and, in most cases, fluorescence under short-wave but not long-wave ultraviolet radiation.