South Africa's Assmang, a subsidiary of diversified miner African Rainbow Minerals (ARIJ.J: Quote), plans to retrench 20 percent of the workers at its Black Rock mine, union Solidarity said on Thursday.

Some 261 workers at the ferromanganese operation would be affected by the layoffs, it said.

The group also blames the planned retrenchments on the effect of the sudden economic downswing, the unstable market conditions, a decrease in demand for their product as well as the strengthening of the rand, the union said in a statement.

(Reporting by Agnieszka Flak)

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