A 373.72-carat chip off the old block recently sold for $17.5 million at Lucara Diamond Corp.'s "Exceptional Stone Tender" in Botswana's capital city of Gabarone. Immense by most standards, the rough gem is actually a broken shard from the second-largest diamond ever discovered — the 1,109-carat Lesedi la Rona. Discovered in 2015, that diamond is […]