Rio Tinto's huge trench cutter sampling rig in position for the first super-deep cut at the Star Diamond property at Fort à la Corne. It cut out a trench 228 metres deep. (submitted photo/Rio Tinto)

By Glenn Hicks

DIAMOND MINING

Rio Tinto drills first bulk sample at diamond site east of P.A.

Jun 18, 2019 | 5:42 PM

Rio Tinto’s huge trench-cutting drilling equipment at the Project Falcon diamond site east of Prince Albert has passed its first big test. However, the mining giant said all-important results won’t be known for months.

The first of 10 bulk sampling holes has been drilled, to a depth of over 228 metres, on Star Diamond Corporation’s Star-Orion South site at Fort à la Corne. Over 700 large bags – or cubes – of kimberlite were extracted and will be stored for analysis along with the rest of the large samples to be drilled in the coming months.

Project director with Rio Tinto Gary Hodgkinson said it was a small but important step for the team, and cautioned it remained to be seen what condition the diamonds were in.

“What we still need to do is ascertain the quality of the sample,” he told paNOW. “We need to be very careful that we don’t crush the kimberlite material so much that we have the possibility of breaking diamonds.”

Hodgkinson said the on-site bulk sample processing plant wouldn’t be assembled and commissioned until October. Only then could the actual diamond results be determined, likely by the end of the year.

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Rio Tinto, has the option on a major stake in the Star Diamond property but has made it clear it could take years to decide if it’s financially viable to operate a full scale mine at the site, with the potential for 700 jobs. Global diamond market conditions would likely also play a role in such a decision.

Keeping the samples safe

As the bulk sampling continues, Hodgkinson said the bulk bags of extracted material would be stored in a secure fenced area under video monitoring and security patrols.

“It’s important for us to demonstrate a chain of custody throughout the entire process,” he said. “[We need] to know the sample material is not going to be tampered with, either by somebody putting diamond material in or trying to take it out.”

He said that was a very low risk but keeping the samples secure had to be demonstrated to all stakeholders.

… this is not a sprint, but a marathon – _{Gary Hodgkinson, Rio Tinto}

Revolutionary technology

This initial technological breakthrough of sampling the kimberlites at such depth has been welcomed by Star Diamond. The enormity of the overburden that covers the kimberlites has been seen as the biggest challenge to accessing the diamonds. The first sample hole intercepted over 117 metres of kimberlite situated more than 100 metres below the surface.

Senior vice president with the company, George Read said in a statement the successful use of the trench cutting sampling rig had “the ability to revolutionize future bulk sampling and mining of kimberlites, particularly for kimberlites characteristic of the Fort à la Corne diamond district.”

Hodgkinson meanwhile was eager to balance the confidence the team felt with the challenges that lie ahead.

“We do realize this is only one part of the puzzle so we still have a long way to go,” he said. “We talk with our team about the fact that this is not a sprint but a marathon, and we have to pace ourselves very well to go through this, as results will only be towards the latter part of the year.”

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glenn.hicks@jpbg.ca

On Twitter:@princealbertnow