Unlocking stranded gold
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A partnership between the CSIRO and local research company Eco Minerals Research is unlocking new ways to utilise stranded gold deposits in Western Australia, with potential benefits for small miners.
Eco plans to demonstrate a scale model of the cyanide-free process and, after recently producing the first gold, will continue the trial on a range of gold ores.
The collaboration was funded in part through an Australian government Innovation Connections grant, and $860,000 from the Science and Industry Endowment Fund (SIEF), which provides grants in the fields of natural and applied science.
Currently, more than 90 per cent of gold producers worldwide use cyanide in the extraction process.
The Australian technology replaces cyanide with a non-toxic reagent known as thiosulphate, which dissolves the fine gold out of ores at similar rates to conventional techniques.
The method has undergone laboratory testing at CSIRO, with results indicating it can be applied to a range of ore types.
Tough regulations and expensive licences for cyanide use have added to financial challenges for small companies wanting to develop new mines.
A typical cyanide-based processing plant costs around $30 million, whereas the new technology has a capital investment of between $2 million and $2.5 million to build.
Mr Hanna said Eco Minerals, which is the research and technology subsidiary of privately owned WA gold producer Nu-Fortune Gold, had been working towards sustainable and environmentally sound methods of gold production.
He said the CSIRO technology was a launching pad for miners to establish operations at a lower cost.
“The capital required to get into the market and produce a bar of gold is a lot less than what it would be to set up a (cyanide-based) circuit,” Mr Hanna said.
He said CSIRO researchers had been developing the technology over a 10 to 15-year period, and the first field production of cyanide-free gold was a great success for WA.
Paul Breuer, principal research scientist in mineral resources at CSIRO, told Business News the technology had been developed to assist small mines access low-grade, uneconomic or stranded deposits of gold that major companies found unviable, and wasn’t intended to compete with cyanide production.
“You need a big deposit to support such a big plant, and they’re few and far between,” Dr Breuer said.
“So you’re getting more and more stranded small gold deposits, and we’re trying to open that market back up.”
He said restrictions placed on cyanide in some areas meant identified gold deposits weren’t being utilised.
Mr Hanna said cyanide use could also be environmentally harmful and even disastrous, particularly around waterways and heavily populated areas.
“The cost of pollution and clean-up is massive,” he said.
“If it spills in the waterways, some places will have $200 million to $300 million in clean-up.”
Cyanide processing has already been restricted in several Australian states and territories, including Victoria and the Northern Territory, as well as some US states.
As bans began to take effect, Mr Hanna had seen demand rise for cyanide-free product.
Dr Breuer said cyanide-free processing could allow small mines to access markets in banned areas, and continue to produce gold less remotely.
Mr Hanna and Dr Breuer both see an initial opportunity for cyanide-free gold, saying some jewellery companies had already flagged interest in paying a premium.
However, Dr Breuer expects the construction of a significant number of cyanide-free plants will eventually result in market saturation.
Despite this, he said a sustainable market for cyanide-free gold could be developed if small mines were permitted to uncover stranded deposits.
This would provide a safe option for densely populated areas, and give possibilities to places where cyanide use had been banned.
“We’re not proposing that we’re a replacement for cyanide,” Dr Breuer said.
“What we’re offering is a process that could potentially fill the void where cyanide can’t be used, or is not economic to be used.”