A geology student who stole a gold-encrusted drill core from one of Australia's biggest gold mines wanted the rock sample as a "memento" and desk ornament, a court has heard.



Key points: Joshua Joseph Welsh pleaded guilty to one count of stealing as a servant

Joshua Joseph Welsh pleaded guilty to one count of stealing as a servant The 22-year-old geology student was working at St Ives gold mine in WA

The 22-year-old geology student was working at St Ives gold mine in WA Welsh received a suspended $500 fine and was granted a spent conviction

Joshua Joseph Welsh, who is in the third and final year of a bachelor degree at the WA School of Mines, pleaded guilty to one count of stealing as a servant in the Kalgoorlie Magistrate's Court on Monday.



The 22-year-old, who is the son of a senior police officer, received a $500 fine, suspended for six months, and was granted a spent conviction — but now faces the prospect of being kicked out of university.

Welsh souvenired the rock sample while working as a geology assistant at the St Ives gold mine near the Goldfields town of Kambalda, about 600 kilometres east of Perth.



His duties included sorting and cataloguing drilling samples, and he committed the offence in the last week of a month-long stint at St Ives before returning to complete his studies.



The court heard Welsh pocketed a sample containing specks of visible gold on June 17.



The sample was reported missing on June 18 and detectives from the Kalgoorlie-based Gold Stealing Detection Unit attended St Ives on June 19.



Welsh confessed to police and was arrested; a subsequent search of his Kambalda property saw the sample recovered.

Geologists spend their days poring over rows and rows of drill core in the hunt for new discoveries. ( ABC News: Jarrod Lucas )

Student wanted keepsake



Defence lawyer Paul Gazia told the court his client conceded he had made a "stupid mistake" and that he should have sought permission first.



"He admitted to taking the sample which he wanted as a memento of his time working at the St Ives gold mine," Mr Gazia said.



"He admits it's serious, given it was taken from a gold mine, and he was working in an entrusted position.



"He's taken the sample of rock with specks of gold to keep on his desk … to keep him motivated to finish his studies."



In applying for a spent conviction, Mr Gazia said it would be a "crying shame" that a young man with potential would not be allowed to finish his degree or enter the mining industry.



He said the former scout leader had no prior criminal record and was heavily involved in charitable causes, including Relay for Life.



The St Ives gold mining operation at Lake Lefroy, near Kambalda. ( Supplied: Gold Fields )



A reference tabled in court from Stephen Blechynden, who was Welsh's supervisor at St Ives, described him as a "committed employee" who "did the hard yards" and "often stayed back after hours".



Welsh's father also provided a reference to the court.



Police prosecutor Sergeant Jodie Mills did not oppose a spent conviction, saying Welsh had admitted the theft straight away.



"He'll be blacklisted from St Ives gold mine anyway," Sergeant Mills said.

"So that's something he'll have to live with."

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'Silly mistake'



During sentencing, Magistrate Brie Ayling described Welsh's actions as an "aberration".



"I am told if they were to put a monetary value on it, it would be around $20," Ms Ayling said.



"It's not a large amount, but any stealing from an employee is a breach of trust.



"Employers have the right to go about their business without thinking people are going around putting things in their pockets."



Specimens containing visible gold are extremely rare. ( Supplied )

Ms Ayling granted the application for a spent conviction as it would have harmed Welsh's prospects of gaining employment in the mining industry.



"It was a silly mistake … you're 22 years old and you have a long working life ahead of you," she said.



"I consider you unlikely to come back to court again."



The rock sample will be returned to the owners of the St Ives gold mine, South African mining giant Gold Fields.

The company has blacklisted Welsh from its operations around the world.



The ABC has sought comment from Curtin University, which operates the WA School of Mines at its Bentley and Kalgoorlie campuses.