The second-largest diamond ever found - a rough 2,492-carat stone - has been unearthed in Botswana at a mine owned by Canadian firm Lucara Diamond.It is the biggest find since the 3,106-carat Cullinan diamond, found in South Africa in 1905 and cut into nine separate stones, many of which are in the British Crown Jewels.The diamond was found at Karowe mine, about 500km (300 miles) north of Botswana's capital, Gaborone.But lets talk about exploitation