Austral said workers from Unions No. 1 and No. 2, which together represented 261 of the 370 unionised employees at the mines, went on strike after seven days of talks failed to reach agreement on a new three-year, collective labour agreement.
It said the remaining union, which represented mine supervisors, had accepted the company's proposal during the March quarter.
CEO Stabro Kasaneva said Austral believed its proposal was fair and in line with its size and current financial situation.
"We and the union's representatives are making our best efforts to reach an agreement soon," he said.
The Australia-based company reported a cash balance of US$6.6 million at March 31, and borrowings and financial leases of $13.8 million.
It was expecting to produce 55,000-60,000oz gold-equivalent at its Guanaco/Amancaya complex this year but said last month it was currently unable to determine the potential impact of the measures taken to de-risk the impact of COVID-19 on annual guidance.
Guanaco/Amancaya produced a combined 17,096 ounces gold-equivalent in the March quarter, 5% less than the December quarter but 33% higher than a year earlier, at an all-in sustaining cost of $893/oz Au-eq.
Amancaya is about 75km from Guanaco, which is lies about 220km southeast of Antofagasta.
Austral's Casposo mine in Argentina was put on care and maintenance in 2019 and it has a circa 26.5% stake in the Rawhide mine in Nevada, plus exploration projects in Chile and Argentina.
Its shares were unchanged at A15c in morning trade and at C14c yesterday in Toronto, near the top of a one-year range, capitalising it about A$84 million (US$54 million).
