THE GREAT PRAIRIE DIAMOND HUNT

A few years ago, the only diamonds near Prince Albert, Sask., were the ballfields of local little league teams or the sparkles from sunlight on the crystal-clear lakes. But in the past year, the whisper of wind through wheat fields has been drowned out by the growl of drill rigs. In the local bars, talk has shifted from the weather and the crops to rumors of diamond mines.

Exploration companies have staked almost 1,400 claims totalling more than 900,000 ha near Sturgeon Lake, 40 km north of Prince Albert. Leading the way is tight-lipped Monopros Ltd., the Canadian subsidiary of De Beers Consolidated Mines. De Beers has stalked the elusive gem around the world, from its home country of South Africa to steamy South American jungles and parched Australian deserts.

And where De Beers goes, others follow. Snatching up the land around the Monopros claim, Saskatoon’s Claude Resources alone has more than 240,000 ha of claims and a number of joint-venture arrangements. Gold mining giant Corona Corp. has optioned 13,600 ha from Claude and already has reported encouraging drill results. The first hole Corona drilled on the claims intersected kimberlite, the most common host rock for the mineral. Intitial tests by Lakefield Research of Peterborough, Ont., showed it to contain diamonds, but neither the quantity nor the quality of the deposit could be determined.

Uranerz Explorations, a subsidiary of Uranerzbergbau gmbh of West Germany, also has staked land in the area. Normally a uranium and gold miner, Uranerz missed by an ace an immense find in Australia when, in the 1970s, it dismissed as worthless its uranium claims there. In 1979, Australia’s Ashton Joint Ventures took another look at the former Uranerz claims and discovered the Argyle deposit, now the world’s largest diamond mine.

It’s far too early to tell if Prince Albert will host another Argyle, but diamond experts (traditionally secretive) are excited. “Right now, the Saskatchewan claims are the hottest diamond prospect in North America,” says Chris Jennings of Corona, as he displays photos of the latest drill core from the company’s exploration program near Sturgeon Lake.

The South-African-born Jennings was hired by Corona in February, 1988, as senior vice-president of exploration. He brings to the company a lifetime of experience and an infectious enthusiasm for diamonds. The shelves of his office are heavy with books of diamond lore and the geology of diamond deposits. He has travelled the world in search of diamonds and is responsible for significant finds in Botswana. Now he wants to add a Canadian mine to his collection.

“The prospects for anyone finding a diamond mine are extremely good,” says Jennings. “De Beers has been rapidly drawing down on their stockpiles (over the past few years). The Kimberley mines are on their last legs.”

Kimberley, South Africa, was the site of the first major diamond mine in 1866 and lent its name to the most common host rock for diamonds. Kimberlite is a blue-green, highly serpentized peridote. Of volcanic origin, it forms deep in the earth where immense pressures and temperatures form the diamonds. Kimberlites extrude to the surface in narrow pipes and sills and often occur in swarms of several dozen.

Kimberlite is rare — only about 5,000 occurrences are known worldwide. Even more rarely does it contain diamonds. About 10% of kimberlites host diamonds and in fewer than 1% are the deposits economic to mine. But the long odds haven’t discouraged prospectors.

Early Canadian diamond-hunters had one tantalizing diamond and tens of thousands of square kilometres to search for the next one. The 33-carat Peterborough diamond (one carat equals 0.2 g) was unearthed near Peterborough, Ont., sometime before 1920. Rough and broken, the diamond was of little value. But if there was one diamond, there had to be more.

The Peterborough diamond and the Jarvi diamond (a gem quality, 0.255- carat stone found near Timmins, Ont.) were both found in glacial till. The dozens of alluvial diamonds found near the turn of the century in the northeastern U.S. were also washed out of till. The diamonds, it was speculated, originated in kimberlite in northern Ontario and had been eroded and carried south by glaciers.

Since kimberlite pipes are small, it is unusual for them to be exposed in outcrop. This is especially true in parts of northern Canada where a blanket of till, tens of metres thick, drapes the land. Prospectors had little choice, therefore, but to search for clues of diamond occurrences in the till, then follow the trail back up-ice to where a kimberlite might be buried.

It’s not easy. The handful of diamonds found don’t leave much of a trail and, since they are so resistant to abrasion, it is difficult to tell whether the glaciers carried them a thousand metres or a thousand kilometres. Indicator minerals for kimberlite such as pyrope garnets, ilmenite and chrome diopside can also be used, but these present their own difficulties. Unlike the constant grinding and polishing characteristic of the alluvial sediments that betrayed the huge Australian and African finds, glacially transported sediments are irregularly abraded. Again, the geologist can’t tell how far up-ice the source might be.

Four times the ice sheets have come and altered the landscape, shifting and redepositing till — leaving geologists with an enormous and complex jigsaw puzzle. “It’s like putting together a detective story,” says Jennings. “You have to piece together layer upon layer of deposits to get the full story.”

Johannes Brummer, another South African-born geologist who specializes in diamonds, agrees. “Glacial drift is the biggest problem we have and the least understood. For 20 years, I’ve been urging the government to research glacial drift, but I’ve been the lone voice in the wilderness.” Now, however, Brummer’s knowledge of diamond-mining is much in demand.

Despite the difficulties, diamond- hungry prospectors persevered. As far back as 1899, geologist William Hobbs speculated that the glacially deposited diamonds originated in the James Bay lowlands at the apex of a fan of glacial dispersion. Extensive drilling was conducted there in the 1960s and although kimberlites were found, none contained diamonds.

Yet interest remained high. Kimberlites were discovered on Somerset Island, N.W.T., in Quebec’s Eastern Townships and, most unusual of all, 30 km west of Montreal on Ile Bizard in the St. Lawrence River.

The Ile Bizard find was made by four students from McGill University in 1967. The area was drilled by the Canadian Rock Corp., a forerunner of Monopros and another De Beers subsidiary. But like so many other promising claims, the pipe turned out to be barren, and De Beers turned its attention elsewhere.

An abandoned gravel pit was the site for the 1985 Monopros find in Saskatchewan. When the gravel reserves were exhausted, the contractor uncovered an unusual dark blue rock at the bottom of the pit. Geologists from Monopros recognized the rock as kimberlite, staked the land surrounding the pit and began to drill. A small processing mill was built on- site but was later moved to an inconspicuous warehouse in Prince Albert. Late last year, Monopros confirmed to the Saskatchewan government that it had intersected kimb erlite on the property and that several microdiamonds were found, but it tagged the deposit as “unlikely to be economic.”

Yet, far from abandoning the claims, Monopros remains active. So does Claude, Corona and Uranerz.

“The geological setting is the single most important feature of the (Prince Albert) bet,” says Peter Gummer, vice-president of minerals for Claude Resources. In contrast to the reticence o
f others involved in the diamond business, Gummer betrays his excitement over the claims. “This is not just pie-in-the-sky. Once it goes public, it will be the most explosive play going. Indications are that it’s one of the largest swarms ever found. The great thing is that the kimberlite pipes are magnetic and are coming up through 3,000 ft of non-magnetic sediments — shales and limestones. When you fly an airborne survey you have immediate definition of the anomaly. Costs are as low as $2,000 per anomaly.”

The ease of exploration in Saskatchewan amazes Gummer. In the shield country of the James Bay lowlands where so much exploration has already been done, the distinctive magnetic signature of kimberlite is masked by a myriad of other conductors.

Then there is the till. Drilling through 50 m of this unsorted material adds a lot to the costs of any diamond drill hole. Gummer was pleasantly surprised to find that the till cover in Saskatchewan is not nearly as thick as was believed. Originally, it was thought that the bedrock of the region was a peneplain overlain by many metres of overburden, but drilling has indicated that the bedrock is instead sculpted into a series of east-west-oriented valleys with a relief of 100 to 200 ft. The cores of the hills seem to be kimberlite, Gummer explains, and the hill crests are thinly covered with till. Drilling costs are as low as $5 per ft and small rotary drills can be used to outline the pipes prior to bulk sampling with larger-diameter drills.

“It’s just amazing how far dollars go out here,” Gummer says. “Remember, this is prairie land. Access is easy and all the necessary infrastructure — roads, power, towns — is in place.”

He remains undiscouraged by the low percentage of economic deposits. “The figure given is that one in 100 kimberlites is economic, but stats fool a lot of people. What’s important is the number of pipes you have. A producing swarm may have one, two, a half-dozen or even 10 mines. The only way to get a swarm is to stake a large area, which is exactly what we did. If one of the kimberlites turns out to be diamond-bearing, then there is probably more. It then becomes a matter of establishing grade.”

Establishing grade is not as easy as it sounds. Compared with gold ore, diamond grades seem impossibly low. The best South African mines grade one part per billion by volume. In a typical deposit, 250 tons of ore must be mined to produce a 1-carat gem stone. Simply determining the grade of the deposit requires about 5,000 carats of diamonds. The economic potential of a deposit depends as much on the quality of the diamonds as it does on their quantity, so samples must be sent to independent appraisers who check the color, clarity and carat weight of the stones. For this, a huge initial bulk sample is needed and this often necessitates an on-site mill.

In the mill, the ore is crushed and the heavy minerals concentrated by gravity and centrifuge. The concentrate travels along a conveyor belt to where it passes under an x-ray beam. Diamonds exhibit flourescence under x-rays and when this is detected, a blast of compressed air blows the ore on to another conveyor belt, further concentrating it. This ore then passes over a grease table which extracts the diamonds. It’s a long, costly process and many of the jealously guarded secrets of the business involve shortcuts to det ermine ore grade. If a company can decide early that a kimberlite is likely to be uneconomic, the time and expense of bulk sampling can be avoided.

It is this knowledge that gives a company like Monopros an advantage over smaller Canadian companies. “Diamond exploration requires considerable expertise — expertise that takes years to build up and costs millions of dollars,” says Corona’s Jennings. Johannes Brummer states it more plainly: “Knowledge is power. If you have information, why share it?”

In an effort to help Canadian companies along, the Geological Survey of Canada has commissioned an open- file report that collects the knowledge and experience of a number of companies in one data base. The project was proposed and carried out by C.F. Minerals of Kelowna, B.C., and its president and chief geologist, Charles Fipke.

The key is the kimberlitic ilmenite and pyrope indicator minerals that are much more abundant than diamonds and, therefore, easier to identify and study. By determining the pressure and temperature at which these minerals formed, it is possible to determine if conditions were favorable for diamond formation.

Fipke is also president of Diamet Minerals, a company actively exploring for diamonds. Diamet has found another diamond source rock, lamproite, high in the Rocky Mountains 60 km north of Golden, B.C. Diamet’s Jack claims are the first proven lamproite occurrences in Canada.

Lamproite is a potassium/silica-rich volcanic rock related to kimberlites. A few lamproites were known to bear diamonds, including the Prairie Creek deposit in Arkansas. Prairie Creek has yielded gem-quality diamonds as large as 40.8 carats and would probably be mined today if it wasn’t situated in a state park. Lamproite would probably always have been regarded as a poor cousin to kimberlites had it not been for the giant Argyle find. Situated, coincidentally, near the town of Kimberley, Western Australia, the lamproite that hosts the Argyle mine will yield more than 35 million carats of diamonds this year.

Despite the breakthroughs in diamond exploration in Canada, there are those who remain convinced that the big find will still be in the James Bay lowlands. This spring, Aurogin Resources drilled seven kimberlite targets on properties near Kirkland Lake optioned from Morrison Minerals. Nothing was found, but Aurogin President Dave Rogers remains undaunted.

“Sure the excitement is out in Saskatchewan — if you want to follow the crowd. But there are other places. I’m not a diamond expert, but I’ve been interested in them ever since I left school. If I see something interesting, I go in and check it out.”

No one knows if the current flurry of diamond fever will make Canada a major producer or simply reinforce the unenviable reputation now implicit in the phrase: “as false as a diamond from Canada.” But after years of fruitless exploration, the determined optimism of today’s diamond- hunters is convincing.

Says Jennings: “Someone in Canada is going to find an economic diamond mine. It would be nice if Corona was that company. Blair Crawford, B.Sc., is a regular contributor to The Northern Miner newspaper.

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