(REUTERS) -- Harmony Gold, South Africa's third-largest bullion miner, said on Tuesday it would consider a Hong Kong listing once its massive Wafi-Golpu project in Papua New Guinea is up and running in around 5 years time.

We would certainly look at a Hong Kong listing, said Mashego Mashego, an executive director at Harmony.

Speaking to Reuters during an underground visit at Harmony's Doornkop mine west of Johannesburg, Mashego said the Wafi-Golpu copper-gold project should cost between $3 billion and $5 billion to develop.

The company has previously said it could cost up to $4 billion. It will be responsible for half the total amount as the project is a 50-50 joint venture between Harmony and Australia's Newcrest Mining.

We will have a far better idea of the potential and costs of Wafi-Golpu in June when the pre-feasibility study is completed, Mashego said.

Wafi-Golpu will be Harmony's second operation in Papua New Guinea. Its Hidden Valley mine already contributes eight percent to the company's production.

Wafi-Golpu is seen producing between 400,000 ounces to 700,000 ounces of gold and 100,000 tonnes to 200,000 tonnes of copper per year and is key to Harmony's strategy of diversifying away from its South African base.