January 15th, 2021

Sweetgrass diamonds? Maybe, but don’t count on it

By Tim Kalinowski on January 5, 2018.

Example of diamond found at the kimberlite deposits in the Buffalo Head Hills area in northern Alberta. According to the Alberta Geological Survey, it is possible, perhaps even likely, similar diamonds exist in minute quantities in the Sweetgrass Hills in southern Alberta and northern Montana.--SUBMITTED PHOTO

tkalinowski@medicinehatnews.com @MHNTimKal

There may be diamonds in them there Sweetgrass Hills, say two experts from the Diamond Exploration Research Training School at University of Alberta, but they would be incredibly hard to find.

“If you just took a really basic look at the geology there,” says Graham Pearson, Canada Excellence Research Chair at the school, “there are some very attractive aspects, that if you were starting from scratch at exploration, you might think were favourable.

“Diamonds generally form in very old (three-billion-year-old) pieces of mantle which underpin crustal rocks. The crustal rock is old enough in the Sweetgrass Hills area, but the problem is research being done on the deeper, underlying roots of that area seems to suggest some dramatic heating event happened at some point in its history that might have been likely to destroy any diamonds that once were present.”

Pearson’s colleague Anetta Banas explains most diamonds are found in kimberlite deposits emanating from ancient volcanos deep within the earth, but diamonds can be exceedingly difficult to pinpoint even in primary deposits, (where the diamonds are coming directly up to the surface from a volcano 200 km below), which is why most explorers rely on the discovery of larger surface deposits of other indicator minerals such as garnet or chromite instead.

What you see in the Sweetgrass Hills, says Banas, are more likely secondary deposits of these indicator minerals, which could have been transported there by vast geological forces from a huge distance away.

“Then you have to put the puzzle back together of how those surficial deposits got to where they are,” says Banas. “The higher the proportion of indicator minerals in an area, the better chance you will find diamonds. We do find those surficial indicators in the Sweetgrass Hills, but there is just a much higher percentage of them in the Buffalo Head Hills in northern Alberta, which is why recent exploration efforts have been more focused there.”

Small companies in Alberta have traditionally driven diamond exploration, and those companies are having trouble attracting investment dollars — which is why no deeper exploration of the diamond potential of Sweetgrass Hills is likely to occur in the near future, says Banas.

“It has kind of fallen by the wayside lately because of the tough economic times,” she says. “Diamonds in Alberta were explored for by junior exploration companies. These companies for the past 10 years have had a hard time raising (investment) money, and that has really put a damper in the diamond exploration business.”

“It is very expensive because you are really tracing ultra-trace components,” agrees Pearson. “You need a huge amount of research on the ground chasing down these surficial deposits, tracking glacial chill and stream sediments, to even find indications of the diamonds.”

The long and the short of it is, says Pearson, don’t expect to be walking around the Sweetgrass Hills and stumble on diamonds.

“There are volcanic rocks in the Sweetgrass Hills, but they are not true kimberlites,” he says. “There are surficial indicator minerals, however, which are associated with diamonds … But it becomes a treasure hunt to track back from surficial deposits to where the primary deposit is.”

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