PERTH (miningweekly.com) – ASX-listed Oz Minerals on Monday revealed that gold trials at its Prominent Hill mine, in South Australia, had confirmed the significant value of existing stockpiles at the mine.

A one-week trail was conducted at the Prominent Hill mine during December, processing existing gold ore stockpiles in a blend with copper ore. The blended ore contained some 60% gold ore, which was indicative of the expected plant ore feed from 2020 to 2022.

Oz Minerals reported that the trial was conducted to assess the impact of the high gold ore blend on plant throughput and recovery, with the results surpassing a similar trial held in 2013, and highlighting the potential optimised circuit that could push throughput of 60% gold ore to about 9.5-million tonnes a year.

At the end of June last year, Oz Minerals had a gold ore stockpile with an estimated ore reserve of 11-million tonnes, grading 0.7 g/t gold, 2.4 g/t silver and 0.10% copper.

As part of the mine plan to prioritise copper production and maximise the efficiency of the openpit mining contract, while keeping the processing plant at near or full capacity until at least 2022, Oz Minerals had stockpiled its significant gold ore as a by-product of its copper mining activities.

“These strong trial results reaffirm our ability to run Prominent Hill at or near full capacity until 2022,” said MD and CEO Andrew Cole.

“The cost of building this stockpile has already been incurred, so we expect to generate significant cash flow from processing the stockpile in addition to our underground ore in future years.”

Meanwhile, Oz Minerals on Monday confirmed that it was planning to shed nearly 100 jobs at its Prominent Hill mine over the next few months, as openpit operations neared completion.

"As the open pit reaches its final depth, the amount of waste rock relative to the amount of ore is decreasing and the space in which the equipment can move is reducing," the company said in a statement.

"[It] means less equipment and people are required,” the company said in a statement to Mining Weekly Online.

The company and its contractor were supporting staff through the transition.