The Portuguese Diamond at 127.01 carats is the largest faceted diamond in the National Gem Collection. Under ultraviolet light, this diamond glows bright blue, a phenomenon called fluorescence. In 1997 it was graded by the Gemological Institute of America (GIA) as M (faint brownish-yellow) in color and VS-1 (very slightly included) in clarity, with very strong blue fluorescence. The apparent cloudiness in the stone is actually the fluorescence that is so intense it is visible even in daylight or incandescent light. In fact, if not for the fluorescence, the diamond would appear slightly yellowish. Its near flawless clarity and unusual octagonal emerald cut make it one of the world's most magnificent diamond gems. The diamond owes its name to a legend that claimed the diamond was found in Brazil in the mid-18th century and became part of the Portuguese Crown Jewels. There is no documentation, however, that substantiates a Brazilian origin or connection to the Portuguese royalty, nor is it clear where or from whom this story originated. The actual story is that in February 1928, Peggy Hopkins Joyce, a glamour girl and Ziegfeld Follies starlet, purchased the diamond from Black, Starr & Frost, mounted on a diamond-studded platinum choker. She traded a $350,000 pearl necklace and $23,000 in cash for the piece. The jewelry firm indicated that the diamond was found at the Premier Mine, Kimberley, South Africa, in 1910, and that Black, Starr & Frost obtained it shortly after its discovery as a cushion-cut stone weighing almost 150 carats. The diamond was later fashioned into its present shape, known as an Asscher cut, at 127.01 carats. In the late 1940s, the diamond was exhibited throughout the U.S., apparently for sale, and was touted as the "World's Largest Emerald-Cut Diamond." It finally sold in 1951, when Harry Winston acquired the Portuguese Diamond from Peggy Hopkins Joyce. For the next several years it traveled around the U.S. as part of Winston’s "Court of Jewels" exhibit. In 1963, the Smithsonian acquired the diamond from Mr. Winston in exchange for 3,800 carats of small diamonds. The magnificent Portuguese Diamond is on display in the Gem Gallery at the National Museum of Natural History.