LONDON – Turns out the largest diamond discovered in over a century may not be worth all that much. The tennis ball-sized Lesedi la Rona failed to find a buyer Tuesday, a disappointing result for a stone which had been described as “the find of a lifetime” by David Bennett, chairman of Sotheby’s jewelry division. The diamond was unearthed in November in Botswana at a mine owned by Canada’s Lucara Diamond Corporation.