Researchers unearth 'tectonic events' that formed Canadian sapphires

Treasure-hunting Canadian researchers say they have figured out how to find sapphire deposits by identifying the exact sequence of geologic events that create the sparkling gemstone.

To date, Canada's only significant deposit of sapphires is one that was discovered near Kimmirut, on southern Baffin Island, Nunavut, in 2002.

The quality of theBeluga sapphires produced from that deposit can be so high that they don't have to be heated to intensify their colour and clarity, unlike nearly 99 per cent of sapphires.

They're goodenough that 48 of them, totalling 10.19 carats, were used to adorn a ceremonial brooch presented to Queen Elizabeth earlier this month by Governor General David Johnstonto mark her sapphire (65th) jubilee on the throne.

The Geological Association ofCanada says the geological setting of the region is similar to that of the gem-producing areas of Kashmir and Myanmar, where some of the world's most valuable stones originated.

But would-be gemologists who want to explore for more are stuck between a rock and a hard place: sapphires are buried deep in inhospitable Arctic terrain. It's an expensive and onerous proposition to mine them.

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That's why mineralogists at the University of British Columbia studied this gold mine of sapphires.

"The quality and the abundance of sapphire in the Kimmirut area is just off the hook it doesn't come close to anything else in Canada," says Philippe Belley, a grad student in the Earth, Ocean and Atmospheric Sciences at UBC.

Belley, along with associate professor Lee Groat and colleagues, sought to explain how those deposits were formed.

"We found that three pressure and temperature events were all necessary to create sapphires in this type of rock composition," Belley told CBC News.

"These events are related to regional metamorphism when you have big tectonic events that cause changes in rock on a very large scale," he said.

The first created a particular group of minerals; the second partially broke down those minerals into a different group of minerals; and the third was a reaction between the two groups of minerals to form corundum sapphire.

The researchers compared this information to regional data from the Geological Survey of Canada to pinpoint what they say are the most promising areas for sapphire exploration in Nunavut.

Their findings are published in the July issue ofCanadian Mineralogist.

Belley says it's a model that could be used elsewhere in the world.

"Look at the metamorphic history of the area, and if it's suitable for that type of deposit, it's worth looking for the indicator minerals."

One of those indicator minerals was scapolite, which in Kimmirut glows a luminous yellow or yellowish-orange.

Belley said he took samples from a location in New York state where scapolite with the same fluorescence feature is present, and he found pink sapphires though they were not gem quality.

'The gem bug'

One expert says finding sapphires in Canada is like finding a sparkly needle in a tundra haystack, so the information the researchers unearthed is valuable.

"The research they're doing is helping us understand the geological environment in which these sapphires occur," says Brad Wilson, a geologist and gemologist who was on the original Kimmirut exploration team. "It helps people like me who are exploring for these gems narrow in on where we can look and expect to find them."

Gem-quality sapphires range in price from $200 to $2,000 US per carat.

Wilsonsays there is simply no way to estimate what sapphire exploration in Canada could be worth.

"We have many place where corundum has been found but only one in one place where it has been found to be gem quality that's this one, and even this one location has not been fully explored," says Wilson, who is also a gem cutter and dealer. "We don't know what's there, we don't know its full potential. Are there other occurrences waiting to be found? Quite possibly. But the answer is unknown."

And it would take billions of dollars to find out.

"The only way you're going to do this is if you have the passion the gem bug to go and explore. This research is going to help people that want to go and look."