John D. Block graduated from Princeton University and attended New York University’s Institute of Fine Arts. John joined Sotheby’s in 1970 and spent nearly thirty years with the company as a specialist, auctioneer and manager. When he left Sotheby’s in the year 2000, he was a Vice-Chairman, a member of the Board of Directors of Sotheby’s North and South America, and in charge of the Jewelry and Precious Objects Division. In this role he oversaw all of Sotheby’s business in the important collecting assets of Jewelry, Clocks and Watches, Silver and Russian Works of Art and Vertu.
John played a major role in establishing Sotheby’s pre-eminence in the international jewelry and precious objects markets. He was involved with every Sotheby’s jewelry auction since 1981, including the magnificent jewelry collections of the Duchess of Windsor; Luz Mila Patino, Countess de Boisrouvray; Mrs. Harry Winston; Jacqueline Kennedy Onassis; and Betsey Cushing Whitney.
During his leadership Sotheby’s, worldwide jewels sales rose from $50,000,000 to over $250,000,000. During John’s tenure, many auction records were achieved including:
White diamonds: $16.5 million in May 1995
Fancy Colored Diamonds: $9.9 million in 1996
Rubies: $4.62 million
Sapphires: $2.8 million
Emeralds: $2.10 million
Cultured Pearls: $2.31 million
John was the auctioneer for several of the most celebrated sales in auction history, including jewelry from the Estate of Jacqueline Kennedy Onassis, Andy Warhol, Mrs. Harry Winston, and Betsy Cushing Whitney.
In January 2001, John was appointed C.E.O. for North America and head of International Jewelry for Philips Auctioneers. In December 2001, John achieved a world record for a fancy red diamond. At $781,250 per carat, the red diamond was the second highest per carat at auction for any gemstone.
In 2003, John formed the Block-Guest Group with Alexander Guest, who has had more than 20 years experience in the auction, wholesale and retail areas of the gemstone and jewelry business.
In 2008 the first international diamond fund, Diamond Circle Capital, was listed on the London stock exchange. John was chosen as 1 of 2 evaluators by the funds’ management, which requires quarterly visits to Geneva and London to appraise the funds assets. John resides in New York City with his wife Hilary Cushing Block and their two children.