Despite its name, it would appear that this wonderful 127 carat octagonal cut diamond has no connection to Portugal, but instead is of South African origin. Its name comes from a rumour that it once formed part of the Portuguese crown jewels (in the 18th century) but there is no proof of this. It is more likely it came from a 150 carat cushion cut stone that was refashioned around 1910-15.
In 1924 the diamond was offered for sale by New York Jewellers Black, Starr and Frost, for 300,000 dollars. It was purchased by Peggy Hopkins Joyce, a former model, dancer and socialite, who was engaged fifty times, wed six (she made headlines with her fifth marriage, when she refused to use the word “obey” in her vows!) and collected diamonds with the same élan that she collected husbands.
She traded a $350,000 pearl necklace and $23,000 in cash for the stone. It was worn by her on a platinum choker.
The next owner of the Portuguese diamond was Harry Winston, who bought it from Joyce in 1951. He sold in the early 1960s to the Smithsonian Institute for 2,400 carats of smaller diamonds.
The diamond was graded by the GIA as M colour and VS1 clarity. The clarity grading was due to a slight bruise on one facet, and two small scratches on the table facet – it is fundamentally flawless, and could be easily improved in clarity. It is remarkable for its strong fluorescence, seen in both daylight and ultraviolet light, which led to it being described by Black, Starr and Frost as the largest Blue diamond ever discovered. In fact it is what is sometimes called in the diamond trade as an “overblue”, an old term for white stones with noticeable fluorescence in daylight. Without the fluorescence it would be a faint yellow.
Another interesting feature of the diamond is that it is an almost perfect octagon, giving it a lovely reflection pattern, very similar to an Asscher cut.