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Smithsonian National Museum of Natural History


Virtually all zircon gems have been heat-treated to enhance their colors. Zircons are also known for their great dispersion or fire.
Photo by Greg Polley. Click to zoom.
Catalog Number NMNH G10660-00
Locality Cambodia
Weight 5.96 ct

Gift of Mr Niveet Nagpal in 2010.

Most gem zircons are found as waterworn pebbles in gravel deposits in Thailand, Cambodia, Vietnam, and Sri Lanka. Zircon is also found in Burma, Madagascar, Brazil and Tanzania. It is typically brown, reddish-brown, green or yellow. Since the 1920s virtually all zircon gemstones used in jewelry have been heat-treated to enhance their colors. Heating in an oxygen-free atmosphere produces blue zircons, which can then be heated in air to give a golden color. The treatment can also yield some colorless stones. Colorless zircon outperforms any other mineral imitating diamond. However, its inferior hardness and brittleness reveal zircon as an imposter. Well-cut zircon gems are beautiful, and like diamonds, they are typically cut as round brilliants to best show their dispersion or fire. The most popular zircons are the blue, colorless, and golden gems produced by heating. This beautiful blue zircon weighs 5.96ct and is from Cambodia.



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