Star – Orion South Diamond Project High Value Stones. (Submitted photo/stardiamondcorp.com)

By Teena Monteleone

Diamond Mine

Star Diamond Corp anticipates ‘decades of mining’ at Fort à la Corne diamond district

Jun 13, 2024 | 2:06 PM

Analysis by Rio Tinto Exploration Canada (RTEC) confirms kimberlite located east of Prince Albert in the Fort à la Corne forest has the ability to produce type IIa diamonds, which are among the rarest and most valuable earth-grown diamonds in the world.

George Read, the senior vice president of corporate development for Star Diamond recently spoke about the evaluation and exploration work RTEC did over the course of five years at the project site located about 60 kilometres east of the city of Prince Albert.

“They looked at the economics of and conceptually could prepare a mine with a 72 year mine life and a plan that could produce diamonds for almost all of that time – every year from starting with Orion South, then Star and then Orion North – remembering that Orion North has 500-million tonnes of kimberlite. It’s a huge body,” he said during an interview with CEO.ca. “So, we’re talking of a future project where we can probably have decades of mining.”

Read said he’d like to think shovels could be in the ground within four or five years. Between now and then, another feasibility study will need to be completed.

“We’ve done a lot of work in the past and can build on that work and bring it up to modern pricing to make sure our numbers are correct.”

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A revised mineral resource estimate is expected to be completed within the next few weeks. That provides the foundation to build a pre-feasibility study which Read said could get done as early as next year. A feasibility study would proceed quickly after that.

“There is no additional field work that needs to take place for the pre-feasibility study to take place. We believe we have a vast trove of information both from our past work and the most recent work done by Rio Tinto,” he said.

Extensive work on underground bulk sample, large diamond drilling and core drilling has been done to define the shape size and internal structure of the kimberlite. Read said they’ve recovered over 150,000 diamonds, 15,600 carats all greater than 1 mm in size.

Rio Tinto used a trench cutter bulk sampling tool to recover kimberlite. The machine cut holes that got down 250 metres below the surface and it proved to be very successful.

North Aerial View of the Star-Orion South Diamond Project. (Submitted photo/stardiamondcorp.com)

Read said the Fort à la Corne kimberlite has a unique diamond population with the opportunity to recover very large stones. The most valuable recovered in bulk sampling was a stone just under 12 carats and D colour which is the highest colourless diamond grade. It has a dollar per carat value of over $11,000 per carat. The confirmation of IIa diamonds in the Orion North kimberlite is especially promising. Most diamond mines produce fewer than two per cent type IIa diamonds. Orion North produced more than 63 per cent of type IIa diamonds. Read said that’s a percentage that’s unheard of anywhere. The biggest diamonds ever found in history, one of which was 3,106 carats, were type IIa. They can be the most perfect white or even pink in colour, which then creates enormous value. In the future, Read predicted the economics of the project could be driven ultimately by the mining of large stones.

“One of the exercises Rio Tinto did was they looked at a mining scenario and looked very carefully at the statistics of the diamond size frequency distribution and they said how much rock would you have to extract to get a 100 carat stone and the answer they got out of the statistical exercise was 222,000 tonnes. It would only take about five days of production, so we’d like to say that we could see an exceptional stone (greater than 100 carats) every week, plus a hundred specials – which individually each weigh more than 10.8 carats.

Read said those kinds of statistics have a dramatic effect on the economics of the province because as diamonds rise in carat weight, their value increases exponentially.

“But in addition to that, small diamonds in Fort à la Corne are also unusually valuable,” said Read. “Smalls are usually valued between $5 and $10 a carat overall and in the case of Fort à la Corne, that number goes up significantly between $30 and $50 per carat range and in some cases maybe even more than $50.”

Last year, Rio Tinto transferred all of its interest in the Fort à la Corne project to Star Diamond – choosing instead to focus its global exploration program on metals and minerals. But its work on the project has led Star Diamond to embark on that revised mineral resource which they aim to publish by the end of June.

Read said they don’t want to get too ahead of themselves in what they anticipate, but they assume there will be a positive increase in the mineral resource estimate.

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teena.monteleone@pattisonmedia.com

On Twitter: @MonteleoneTeena