As per industry website, Christie’s International in the current week is expected to place on auction a diamond considered the most valuable stone offered by the company sp far. The diamond is of 35.56-carats, and a fancy grayish-blue stone, mined in India and once owned by King Philip IV of Spain. It is estimated to sell for 9 million pounds ($13.4 million). The diamond has been in the ownership of a private collector since 1964. %% As per Christie’s, the stone is of subtle nature and has a versatile appeal for the way it has been re-cut since the 17th century and for its size, colour, and its historic provenance. %% The auction, to be held in London in the week, will have 212-lots on sale, estimated to generate a value between 15.2 million pounds and 18.7 million pounds.