The rand’s decline against the dollar was raising costs for South African platinum companies operating in Zimbabwe, making the ventures uncompetitive, the country’s mining minister said.

“Simply by the depreciation of the rand, all of a sudden, if you compare Zimbabwe’s platinum mining costs and South African mining costs, despite the depth in South Africa and other things, there is a way in which we are moving towards being relatively uncompetitive,” Walter Chidhakwa told reporters in the capital, Harare.

Anglo American Platinum and Impala Platinum, the world’s top two producers of the metal, have units in Zimbabwe.

The rand has lost 22 percent against the dollar since the start of last year. The drop has pushed up mining costs in Zimbabwe because companies buy most explosives and equipment from South Africa.

Zimbabwe has the world’s biggest platinum reserves after South Africa. While it produces about 430 000 ounces a year, it is refined in South Africa.

Chidhakwa said four companies he did not identify had platinum claims they were “holding for speculative purposes… We are going to ensure that those holding our claims for speculative purposes do not have a place in Zimbabwe.”

Platinum companies are contending with Zimbabwe’s imposition since January 1 of a 15 percent tax on ore exports, in addition to a 10 percent royalty already levied on their revenue.