The Wittelsbach diamond, now the Wittelsbach-Graff diamond @ the Smithsonian Institution in Washington

The Wittelsbach diamond (shown in 2008 before recutting) was part of the dowry for the Infanta Margarita Teresa. Copyright 2009 The New York Times Company

The Infanta Margarita Teresa. Musée du Louvre, Paris

For more than a half-century, one of the world's most celebrated diamonds, the fabled Wittelsbach blue, was not on view. It was once set in the Order of the Golden Fleece ornament, shown here.

A grayish blue diamond taken to Europe in the 17th century from India, it was given in 1664 to the Infanta Margarita Teresa by her father, the king of Spain, eventually becoming a fixture of both the Austrian and Bavarian crown jewels.

Photo: Olivier Laban-Mattei/Agence France-Presse -- Getty Images.

Ludwig I (Louis I) of Bavaria standing beside the Bavarian Crown mounted with the original Wittelsbach diamond.

In December 2008, the Wittelsbach blue suddenly turned up at auction, centerpiece of Christie's London sale of important gems.

Photo: Alastair Grant/Associated Press

The buyer was Laurence Graff, the billionaire diamond dealer, who made a series of startling decisions about the stone. First, he had it recut, reducing it from 35.52 to just over 31 carats, to eliminate the chips and "bruises" inevitable in a stone of its age but also to improve its clarity, brilliance and grade.

Left, Mr. Graff (shown with his wife, Anne-Marie). Photo: Dave M. Benett/Getty Images

Then he renamed it the Wittelsbach-Graff and struck an agreement with the Smithsonian Institution in Washington to display it.

Photo: Chip Clark/Smithsonian Institution

Read "Out of the Blue, Prestige and Riches" by GUY TREBAY http://www.nytimes.com/2010/01/07/fashion/07DIAMONDS.html