African Barrick Gold aims to build an underground operation beneath existing open pits after finding more gold at its North Mara mine in Tanzania. The London-listed FTSE 100 firm declared an initial resource of 370,000 ounces beneath two open pit operations at North Mara, it said in a statement yesterday. The discovery provides “the potential to develop a substantial underground operation at the Gokona and Nyabigena deposits with an attractive grade profile”, the firm said. Further drilling early next year is expected to boost the underground resource to more than one million ounces. North Mara, is one of four mines run by African Barrick in northwest Tanzania. The stock closed up 2.3 per cent at 552p yesterday.