Good Read Y'all. Mule likes it too!
Quality control questions for De Beers - a devil in the details?
Monday, September 13, 1999
VANCOUVER (InfoMine) - The announcement by Kensington Resources Ltd regarding the latest lab results from testing of the kimberlite concentrate samples from the Fort a la Corne diamond project in Saskatchewan has raised questions concerning diamond giant De Beers' South African lab procedures and results. Fortunately for the partners on the project (Cameco Corp, Monopros Ltd, a wholly owned subsidiary of De Beers, and Kensington), the problem with De Beers' Sortex recovery plant has been recognized and steps are being taken to re-examine previously tested samples.
The primary objective of the Fort a la Corne project's 1999 drilling program was to focus on further bulk testing of kimberlite bodies 147 and 220. Both have yielded favorable results from previous testing and required additional evaluation. These and a few other bodies are recognized as having the greatest economic potential on the basis of the data compiled to date. Kimberlite bodies 147 and 220 are reported to contain in excess of 490 and 80 million tonnes of kimberlite, respectively.
The Fort a la Corne kimberlite cluster is one of the largest clusters in the world and contains 71 kimberlite bodies. Thirty-four of the 69 kimberlite bodies tested by drilling contain macrodiamonds. The 1999 program consisted of four reverse circulation airblast large (11ó") diameter holes that were drilled to collect samples from kimberlite bodies 147 and 220 which join with other bodies to form a mega-cluster. Two drill holes were targeted on kimberlite 220 and another two were completed on kimberlite body 147. Approximately 64 tonnes of kimberlite material was retained from a theoretical mass of 87 tonnes from these four drill holes. Concentrating of the minibulk samples occurred at the Monopros facility in Canada.
Technology incorporated into the Sortex recovery plant relies on a diamond's character to typically fluoresce when struck by X-ray light. In the process, heavy mineral concentrate is spread thinly on a conveyor belt and dropped over a small gap. Optical sensors detect fluorescing diamonds and trigger a jet of compressed air that blasts them into a separate collector. The system is preferable to hand sorting in that security concerns (theft of diamonds) are reduced.
However, not all diamonds fluoresce. For example, Trivalence Mining has installed a grease table at their Aredor diamond mine in Guinea to recover the estimated 5% of diamonds that do not fluoresce. Typically, the percentage of diamonds that do not fluoresce is less than 10% of the total.
According to Kensington, Monopros reported the recovery of 58 macrodiamonds (greater than 1 mm) from the 1999 winter drilling X-ray concentrate. This figure was around half the number expected, given previous results for the same kimberlites. As a number of stones were recovered from the 1997 X-ray tailings, all 1999 X-ray tailings were visually examined and a further 69 stones were found, thus increasing macrodiamond recovery by 119 per cent.
In a report to the partners, Monopros wrote: "The most significant factor arising from the 1999 work was the unusually large number of diamonds recovered from the X-ray tailing material from the Sortex recovery plant. Monopros is taking steps to re-examine the entire 1997 Sortex tailings collection in light of the new results. In addition, investigations are under way to fully assess the treatment history of all pre-1999 macrodiamond recovery samples."
This development has prompted the Fort a la Corne joint venture partners to visually resort all Sortex concentrate tailings from 1990, 1991 and 1997. Such a decision suggests that the Sortex concentrate tailings have not been visually resorted.
When the operatorship of the Fort a la Corne diamond project was assigned to Monopros Ltd for the 1998 - 1999 exploration program Kensington noted that Monopros assigned a very experienced team to operate the Fort a la Corne project.
In hindsight it appears De Beer's experience and world class expertise in diamond exploration and project management may not have helped the project that much. It appears that the assumption that a high percentage of Fort a la Corne diamonds fluoresce might have been wrong. In addition, the omition of grease table recovery may have lead to delays and uncertainty regarding previous Sortex results. A well designed early stage orientation program could have determined the character of Fort a la Corne diamonds, especially ones that don't fluoresce. In addition, a program of duplicate samples and check samples could have flagged potential recovery problems with the Sortex recovery machine, if that is where the problem lies.
If the problem lies with the Sortex recovery machine, and goes back as far as 1990 as suggested by the move to resort, the implications are quite staggering. Could the bulk sample results from previous programs on the Fort a la Corne property have been significantly underestimated?
In addition to the Fort a la Corne property, it is understood that Monopros utilizes the South African lab for its other diamond exploration projects. If the Sortex machine is the source of the recovery problems, many of those previously tested exploration projects may have to be re-evaluated.
Could this be why Monopros has yet to discovery any economic kimberlite pipes of it own in Canada despite decades of expensive exploration? Ouch!
The devil is in the details.
By Harvey Klatt - Staff Reporter
harvey@infomine.com
InfoMine?s NewsMine is developed and maintained by ROBERTSON INFO-DATA Inc. Copyright 1999.
E -Mail: info@infomine.com
The information contained in InfoMine's NewsMine is collected from a variety of sources on a "best intentions" basis. Robertson Info-Data Inc. makes no representation or offers no warranty with respect to the adequacy of the information for any particular purpose. In particular any information presented in InfoMine's NewsMine is not a solicitation to purchase or acquire any securities. Use of this service is an acceptance of this disclaimer. Please visit our web site to read our complete disclaimer. |
