Plutonic is the highest-cost of Northern Star's five mines, producing around 79,000 ounces last financial year at an all-in sustaining cost of $1550 an ounce.
The permit marks another key step in the process of moving towards development of the 1.45 million carat diamond resource in the West African country, said the company.
Gold miners in particular have stepped up technology investment within a falling capex budget, as the metal price in producers’ currencies has held up much better than other commodities.