The project is now ready for development, pending finance.
Earlier this month, Orion was granted the water use license.
"Prieska is now positioned to play a major role in the post-COVID economic recovery of the Northern Cape region of South Africa with the development of a world-class base metals mining operation," Orion managing director and CEO Errol Smart said.
"The achievement of this major milestone is testament to the exceptional geological potential and attractive business operating environment that we have found and made our home in the Northern Cape.
"In less than five years we have been able to locate, acquire, drill out, complete a high-quality bankable feasibility study and fully permit a world-class modern mine, to international best practice standards."
Prieska is set to produce 226,000 tonnes of copper and 680,000t of zinc at all-in sustaining costs of US$1.60 per pound of copper equivalent over 12 years.
The project has a post-tax net present value of A$552 million and a pre-tax internal rate of return of 39%.
Capital costs are $373 million. The project has already had about $36 spent on it.
"The receipt of this final approval is a strong foundation for our ongoing discussions with potential financiers of the debt and equity components of the construction financing package and we look forward to being able to update our shareholders on progress over the next few months," Smart said.
Macquarie has been appointed to explore partnership and/or financing options.
Orion had cash of $1.2 million at the end of June, but earlier this month, it raised $6.2 million in a placement to sophisticated and professional investors at 1.7c per share.
Shares in Orion were up 10% this morning to 2.2c. The company has a market capitalisation of $71.3 million.