DIAMOND SPECIAL — Early history of Point Lake kimberlite

The history of the Point Lake discovery — a diamondiferous kimberlite, by Dia Met Minerals (TSE) and joint-venture partner BHP Minerals in the fall of 1991 — began with the exploration for indicator minerals along the Mackenzie River, near Blackwater Lake, some 13 years ago by Diapros Canada, the Canadian subsidiary of De Beers at that time, and by Falconbridge (TSE) and one of its major (indirect) shareholders, Canadian Superior Oil.

While important indicator minerals for kimberlite were discovered, the bedrock source was not located.

Six years ago, Dia Met, under the direction of Charles (Chuck) Fipke (founder and chairman of the company), initiated a heavy mineral sampling program east of the Mackenzie River, and through some pretty tough years, financially, traced the indicator minerals by systematic sampling of glacial debris (eskers, tills and beach sands) up-ice to the Lac de Gras region. Dia Met staked its first claims in the region in 1989 and in April, 1990, identified the Point Lake structure.

Speaking to CBC News in November, 1992, Fipke said: “We were right at end of budget; we had two days of flying and then we were out of money. I was in the front seat navigating the helicopter and we were stopping at each place to put our pegs, our staking pegs, and I just happened to look out the side of the window and the wind had blown the snow off the outcrops sort of on the south side and the north side, and this was broken by this hole, so I made a note of it and we kept on staking and then that evening I decided to cancel the staking, and go to this lake. The ground was all frozen so we had to chip through and just take these pieces of soil, glacial till, and while we were doing it, my son Mark discovered a chrome diopside.”

Four months later, a joint-venture agreement was signed with BHP Minerals, a subsidiary of The Broken Hill Propriety Company — Australia’s largest corporation.

Under the agreement, BHP, as operator, must finance all exploration at a minimum of US$2 million per year through completion of the feasibility study and arrange financing up to US$500 million for the first mine in order to earn a 51% interest. Dia Met will then have a 29% interest (two individuals hold the balance) with its share of the capital cost to be repaid from production proceeds. Dia Met would be responsible for financing its share of capital costs over US$500 million or any subsequent mine developments. This first kimberlite target was located at Point de Misere at Lac de Gras, about 200 km northeast of Yellowknife, N.W.T., under a small lake known as Point Lake (not to be confused with the large “Point Lake” to the west). A single small diameter hole was drilled in September, 1991, intersecting kimberlite between 455 and 920 ft.

The core was analyzed at the laboratory of C.F. Mineral Research in Kelowna, B.C. (owned by Fipke). The results released on Nov. 5, 1991, indicated that 91 diamonds had been recovered from a 59-kg sample, representing a half split of the core over the length of the kimberlite intersection, that is, 465 ft. In February and March of 1992, BHP Minerals (as operator) drilled 37 reverse circulation holes from the surface ice of Point Lake and the bulk sample taken was trucked to Dia Met’s pilot mill diamond recovery plant at Sloan Ranch near Fort Collins, Colo.

On May 22, 1992, Dia Met announced “that diamonds weighing at least 90 carats were recovered from the bulk sample” which amounted to 160 tons. The release added that a few stones were in the 1-to-3- carat range and “that about one-quarter of the diamonds found were likely to be a gem quality”. Further work ensued during the next month with expert examination of the diamonds carried out in San Francisco.

On June 25, a further release was made confirming that the final weight of the diamonds recovered from the 160-ton sample was 101 carats and about a quarter of the diamonds were, indeed, gem quality. The release stated clearly that the gem quality fraction excluded any stones commonly referred to as “near gem” and repeated that a few of the stones were in the 1-to-3-carat range.

Reconnaissance diamond drilling of other pipe targets, generally on the eastern half of the main block of the Dia Met/BHP holdings (which amount to some 840,000 acres), continued through the summer. On Sept. 14, Dia Met announced that the summer drill program, accompanied by mapping, had identified nine new kimberlites in addition to the pipe at Point Lake. On Dec. 8, 1992, the macro/micro diamond contents of core samples were released with excellent results from pipes 92/B and 92/I.

During the 1993 winter/spring season, a bulk sampling (drill) program was carried out on four pipes and on June 21, the results were released. Three months later, on Sept. 21, the results of valuations of the diamonds from three pipes were released, as well as the macro/micro diamond count from three of the new pipes discovered in 1993.

The results from Pipe 93/J (155 macros and 259 micros in 60.5 kg) were multiples of anything seen to date at Lac de Gras and may indeed be a world record for diamonds recovered from core.

— From a Richardson Greenshields research report.