A rare colored diamond and diamond ring. Photo Christie's Image Ltd 2014

Set with a modified cut-cornered rectangular-cut fancy gray-blue diamond, weighing approximately 5.17 carats, flanked on either side by a trapeze-cut diamond, mounted in platinum. Price Realized $1,145,000

With report 16242445 dated 11 January 2014 from the Gemological Institute of America stating that the diamond is fancy gray-blue, natural color, VVS2 clarity; accompanied by a working diagram indicating that the clarity of the diamond may be potentially internally flawless

Accompanied by a supplemental letter from the Gemological Institute of America stating that the diamond has been determined to be a type IIb diamond. Type IIb diamonds are very rare in nature (from our experience, less than one half of one percent) and contain small amounts of boron that can give rise to a blue or gray coloration. An unusual property of type IIb diamonds is that they are semi-conductors and conduct electricity. Historically, the ancient mines of India produced occasional blue diamonds but today the most significant source is limited to the Cullinan (formerly Premier) Mine in South Africa. Among famous gem diamonds, the 70.21 carat Idol's Eye and the 45.52 carat Hope, are examples of type IIb

From the collection of Riki Shaw, a leading advocate for animal rights and rescue. Proceeds from its sale will benefit cage-free animal shelters and the continued fight against animal cruelty.

Christie's. MAGNIFICENT JEWELS, 16 April 2014. New York, Rockefeller Plaza. www.christies.com