By Reuters Staff2 Min ReadFILE PHOTO: An employee works at an electricity cable factory in Baoying, Jiangsu province, China, July 23, 2006.... REUTERS/ Aly Song GABORONE, Botswana( Reuters)-Australia’s Sandfire Resources Ltd said it has been granted a mining licence and can start constructing a copper mine in Botswana’s Kalahari copper belt, as the nation strives to diversify its sources of income away from diamond revenues. The Kalahari Copper Belt, which extends over nearly 1, 000 kilometres(