The oldest diamond is generally considered to be the Briolette of India . Given to Eleanor of Auitaine by Louis VII of France in the 12 th century and to Diane de Poitiers by Henry II in the 16 th century, the 90.38-carat diamond went unseen for hundreds of years until 1950, when an Indian maharaja sold it to Harry Winston, a New York jeweler. Mr. Winston sold it to Mrs. I. W. Killam and then bought it back after her death 10 years later.