PERTH (miningweekly.com) – Dual-listed gold miner Troy Resources on Wednesday reported a series of rock falls at its Casposo gold and silver mine, in Argentina, and said that it had received an environmental permit for its Coruja deposit at Andorinhas, in Brazil.

At Casposo, the miner said that a clay-rich zone around 2 m into the hanging wall initiated a zone of weakness, which resulted in waste material falling into the stope, within the high-grade Inca 1 zone.

The area impacted was directly above the highest grade levels within the Inca 1 zone, and was expected to increase the dilution of the ore with waste, lowering the grade drawn from the stope and delaying the mining of the very high grade ore.

Troy told shareholders that the company was reviewing the mine plan at Casposo to minimise the risk of such an incident re-occurring.

Furthermore, an inspection of the mill liners has resulted in Troy taking the decision to bring forward a six-day maintenance shutdown at the Casposo plant, which had initially been scheduled for early July.

With the maintenance downtime and the rock fall, production for the June quarter was expected to be around 27 000 oz of gold equivalent. However, Troy was unable to comment on how the rockfall would impact full-year production.

Meanwhile, at the Andorinhas mine, Troy was awarded an environmental permit to mine the Coruja openpit deposit.

Ore was currently only being sourced from a limited number of underground shrinkage stopes and low-grade stockpiles.

ASX- and TSX-listed Troy said that the approval of mining at Coruja ensured that sufficient high-grade ore would now be delivered to the processing plant. This would ensure that the operation would continue until the end of 2015, and would likely produce between 27 000 oz and 30 000 oz in that year.

Without Coruja, the Andorinhas operation would have closed in the second half of 2014.

Troy was expected to mobilise a contract mining fleet this month, with first Coruja ore entering the mill feed by the September quarter.