London: It's a rock for the ages. A 3-billion-year-old diamond the size of a tennis ball the largest discovered in over a century could sell for more than USD 70 million, auctioneer Sotheby's said today. The auction house plans to offer the Lesedi la Rona diamond in London on June 29.

The diamond was unearthed in November in Botswana at a mine owned by Canada's Lucara Diamond Corporation. It measured 1,109 carats, the second-largest gem-quality rough diamond ever discovered. Its name means "our light" in the Tswana language of southern Africa.