A 28-year-old West Australian man who processed stolen gold in his grandmother's shed using the toxic chemical mercury has been jailed for 15 months.

Key points: A 28-year-old WA man who processed stolen gold in his grandmother's shed has been jailed

A 28-year-old WA man who processed stolen gold in his grandmother's shed has been jailed He acted as a getaway driver while an unknown accomplice broke into a mill near Coolgardie

He acted as a getaway driver while an unknown accomplice broke into a mill near Coolgardie His lawyer said he had been exposed to mercury which has left him with anxiety and memory loss

The lawyer for Joshua Luke Cross claimed his client has suffered cognitive impairment because of the mercury exposure, including memory loss and increased anxiety.

The former building contractor was sentenced on Friday after breaking into the Burbanks mill near the historic gold mining town of Coolgardie, about 550 kilometres east of Perth, on three separate occasions in December.

The Kalgoorlie Magistrate's Court heard Cross was the getaway driver on each occasion.

An unknown co-accused used a hammer drill to dig up concrete flooring which contained specks of gold, before processing it and selling it for about $19,000.

At one point, they used a vacuum cleaner to collect gold fragments as they chipped away at the concrete.

Cross pleaded guilty to 10 charges in all, including three counts of aggravated burglary, three counts of stealing and one count of trespassing.

The burglary charge could have attracted a maximum penalty of three years' jail, or a $36,000 fine.

The Burbanks mill is 8km south of the historic gold mining town of Coolgardie, WA. ( Supplied: Maximus Resources )

Burglaries involved 'degree of planning'

During sentencing, Magistrate Adam Hills-Wright said the burglaries were "sophisticated", involved "dangerous chemicals", and sat at the "serious" end of the spectrum.

He noted Cross had "sinister intentions" because he had a balaclava on the front seat of his vehicle and had taped over the interior light.

"Clearly it involved some degree of planning and involved forced entry at night," the magistrate said.

"You did not wield the tools but found yourself in company with those who did."

Cross personally sold gold to a Kalgoorlie buyer worth about $4,000, $3,000 and $9,000 on three separate occasions.

Police found receipts for the transactions during a search of a South Kalgoorlie property.

Mr Hills-Wright said the money has not been returned.

A gold nugget discovered near Kalgoorlie-Boulder in WA's Goldfields. ( ABC News: Rhiannon Stevens )

Mercury exposure can cause cognitive impacts

Mercury is considered by the World Health Organisation to be one of the top 10 chemicals of major public health concern, and there is evidence to show it has caused cognitive impacts in children.

Cross' lawyer Kim Samiotis told the court her client has high levels of mercury in his blood and needs specialist treatment in Perth, which she said he would be unlikely to receive in custody.

She tabled medical records in court which showed readings of 169 nanomoles per litre of blood in January, compared with the standard of 0-50.

"He's suffered from anxiety and memory loss," Ms Samiotis said.

"His family noticed a substantial change in behaviour at the time of the offences.

"He very likely wasn't thinking quite clearly … he's had impaired cognition as a result of mercury exposure."

Gold processing to 'supplement Centrelink'

Ms Samiotis said Cross assisted the co-accused by driving them to the mill and processing the gold.

She said he supplements his Centrelink income by processing gold in his grandmother's house for a friend with a legitimate prospecting lease.

She said he received stolen tools as proceeds and the rest of the money was passed onto the co-accused.

The court heard Cross has had a methylamphetamine addiction in the past and was jailed in 2016 for prior burglary and stalking offences.

Mr Hills-Wright said his extensive criminal record was "relevant" in his decision to impose a jail term, particularly after Cross was ruled "unsuitable" for a supervision order.

"It was quite a risk in terms of your own health and the exposure to criminal law for some tools," he said.

Cross will be eligible for parole.

Kalgoorlie courthouse, where the 28-year-old thief was convicted. ( ABC News: Jarrod Lucas )

Gold mines a 'soft target' for thieves

The owners of the Burbanks mill, ASX-listed Maximus Resources, announced earlier this month they have agreed to sell the plant for $5.8 million to Perth-based private company Adaman Resources.

The plant had been shutdown during the period it was targeted by the thieves.

Mr Hills-Wright said he has dealt with several gold stealing cases in recent times.

"Mines sites can be a soft target, particularly gold mines, because they are so isolated," he said.

"It is notoriously difficult to adequately police and protect them because of their size and remote location.