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March-April 2014

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Optically Sector-Zoned (Star) Diamonds from Zimbabwe

In 2010, a new jewelry trend emerged at the Tucson Gem and Mineral Show, one that used lower quality diamonds or diamonds with inclusions in high-end jewelry. These colorful but semitransparent or opaque diamonds are used rough, in rose cut, or more commonly in double-sided polished plates (sometimes with extra facets). In 2011, we first noticed "star" diamonds at the Tucson Gem and Mineral Show; these were sliced plates of colorless diamond with a gray 2-, 3-, 4-, or 6-ray star pattern (fig. 1). These diamonds bear a striking resemblance to those described in a paper by Rondeau et al. (2004) on "asteriated" diamonds of historic significance from India and Brazil. The renowned mineralogists Renée Just Haüy and Alfred Des Cloizeaux originally studied these specimens and kept them mounted on golden pins. They are now part of the collection of the National Museum of Natural History in Paris, France. The market for these star diamonds has increased, and star diamond plates were more popular than ever at gem and mineral shows in 2013. The source of these diamonds is allegedly Zimbabwe, but they were cut and faceted in India.

Dr. John Rakovan, an executive editor of Rocks & Minerals, is a professor of mineralogy and geochemistry at Miami University in Oxford, Ohio.

Dr. Eloïse Gaillou is associate curator in the Department of Mineral Sciences at the Natural History Museum of Los Angeles County and was a postdoctoral fellow at the Smithsonian Institution at the time of this study.

Dr. Jeffrey E. Post is the curator-in-charge of the Smithsonian Institution's Gem and Mineral Collection.

Dr. John A. Jaszczak, adjunct curator of the A. E. Seaman Mineral Museum, is a professor of physics at Michigan Technological University.

John H. Betts is a full-time mineral dealer who has specialized in diamonds during the past decade.

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