The company told local media in December that joint-venture partner Jiujiang Mining Australia had withdrawn from the project and as a result most staff would be made redundant.
About 80 workers are employed at the mine, which is situated in the Woomera Protected Area, a sensitive Australian military facility used for testing missiles.
Cu-River restarted operations at Cairn Hill last year after a production halt in late-2017, with plans afoot to expand again and build a minerals concentrator and other infrastructure.
The miner also had designs on the Snaefell and Tomahawk iron ore deposits, with development there expected to create about 350 jobs over the next seven years.
However, rising tensions with China sparked questions about national security and raised concerns the joint venture might have been electronically eavesdropping since 2010 on the secret defence base, which is supposed to be heavily restricted.
Under the rigorous protective security regime all people entering the WPA are meant to be checked by the Defence Department, and mining is supposed to be done by Australian-controlled companies.