Answer: By A. Sundaramoorthy, former Director General, GSI
For copper the surface manifestation is development green or bluish green malachite stains and gossan, example Rajpura Dhariba, Rajasthan. For gold associated with other sulphides it is development of yellowish stains and development of gossan with boxwork. If gold occur in native form like Kolar Gold field no surface indication except destination and specks of gold in the host rock. Gold is a very tricky mineral. The sampling should be very close because concentration varies widely. Secondly the drilling also done very close may be 100 m intervel. The main thing is sample analysis should be done by fire assay.