“The Blue Moon of Josephine,” fancy vivid blue diamond weighing 12.03 carats, internally flawless, sold for $48,468,158, or $4,028,941 per carat (world auction record for any diamond of any color or a gemstone; world auction record price-per-carat for any diamond or gemstone).

GENEVA, SWITZERLAND — Sotheby’s set a new auction record for any diamond and any gemstone on November 11 when “The Blue Moon of Josephine” sold for $48.5 million at the firm’s sale of Magnificent Jewels & Noble Jewels.” The result works out to a price-per-carat of $4,028,941.

Named after the expression “once in a blue moon,” the rare cushion brilliant-cut stone weighs 12.03-carats. The Gemological Institute of America graded the stone fancy vivid blue (the highest possible color grading for blue diamonds) and declared it internally flawless.

Previously called the “Blue Moon diamond,” the stone was purchased by a private collector from Hong Kong who has renamed the record-breaking jewel “The Blue Moon of Josephine.” The prior auction record for any diamond had been held by the Graff Pink (24.78 carats), which sold for $46.2 million at Sotheby’s Geneva in 2010.

The result for the Blue Moon of Josephine marks a new auction record price-per-carat for any diamond or gemstone – surpassing the benchmark established just last year at Sotheby’s New York by the Zoe Diamond ($3,348,205 per carat) – as well as a new auction record price for any jewel – a title also formerly held by the Graff Pink. This is the first time any diamond or gemstone has reached more than $4 million per carat.

The Blue Moon of Josephine was the star lot in the sale that totaled $139,085,346.