Answer: not many at all.

This makes South Africa focussed Theta Gold Mines (ASX:TGM), which has just increased its resource to more than 6m oz all up, a bit special.

The company’s flagship project is the Theta project, about 370km east of Johannesburg.

In addition to growing the resource, Theta Gold has also delivered a maiden 205,000oz reserve.

Typically, reserves refer to discoveries that are valuable and economically/technically feasible to extract, while resources are ‘potentially’ valuable.

Theta wants to start unlocking this 6m oz resource base, starting with open cut mining. That’s where the 205,000oz reserve comes in.

It  underpins Theta Gold’s newly released feasibility study, which anticipates a five-year mine life producing about 40,000oz a year.

Construction costs of about $40m are very manageable, while all in sustaining costs of production – about $1103/oz — are some of the lowest in South Africa. Check this out:

Theta Gold reckons it can make about $95m in free cash over the initial life of the mine.

“Despite only a small part of the resource base being converted into a mining reserve, the Feasibility Study confirms that the project has very favourable economics and viability,” chairman Bill Guy says.

“The remaining unconverted resource will be subsequently drilled out and I expect that further resources will be converted into reserves.”