Dec '08/Jan '09


A marriage of micro and macro: SRC’s high-security diamond laboratory

By M. McCubbing


Glove boxes ensure no hands touch the diamonds.

The Saskatchewan Research Council (SRC) has a long and distinguished record of supporting the mining and mineral processing industry with quality research and applied innovation. SRC’s focus areas have included slurry pipeline research, chemical/geochemical analysis and welding technology, to name a few. One current initiative has been to advance their capabilities in establishing high-quality analysis for the diamond mining industry. The following article from an  SRC publication descibes this effort.

Ore quality analysis in the diamond industry is a high-technology business demanding exacting standards of accuracy and security. In 2007, the SRC opened a large high-security diamond laboratory in Saskatoon’s north industrial area, not far from SRC’s recently opened first dense media separation (DMS) plant. The laboratories conduct micro diamond analysis on core drilling samples, while the DMS plant looks for macro diamonds in bulk samples from large-diameter drilling.

A great deal of experience and expertise went into the construction and commissioning of the new DMS plant. The plant exploits the high specific gravity of diamonds to separate them from lighter material. Ore is crushed, de-slimed and screened to remove fine material. It is then mixed with a dense medium and put through a cyclone to separate the heavier material.

As well as meeting burgeoning demand in Saskatchewan, the operations also serve a growing list of international clients. SRC built on their capabilities in micro diamond analysis to spur the move into macro diamonds, and industry development also demanded it.

The divide between micro and macro diamonds is 0.50 millimetres. Recovered micro diamonds can be as small as 75 micrometres. This is reflected in the ore volume each operation handles. The micro lab processes samples ranging from a few kilograms to a few thousand kilograms, while the DMS plant can handle ore samples of up to 500 tonnes. Macro processing cannot recover as finely as micro analysis, but the odds of finding larger stones increase as more rock is processed.

The micro diamond labs cover a working area of 1,375 square metres, with 80 kilns in operation, and are able to process two tonnes of samples per week, using a caustic fusion process. This makes it the world’s largest commercial lab that undertakes micro diamond extraction. SRC has developed a reputation as one of the best micro diamond labs in the world, and is now seeking to acquire similar repute on the macro diamond circuit too.

The marriage of macro and micro diamond processing capabilities helps SRC provide all-in-one, one-stop shop services for exploration, from grassroots till sampling to micro and macro diamond extraction. This is significant because macro analysis is essential to proving a deposit and deciding whether costly mine development is justified.

SRC’s high-security diamond services became even more secure with the addition of a strictly controlled, red-level process to the DMS plant. According to Bernard Gartner, SRC’s geo-analytical laboratories manager, “A red-level facility means absolutely no hands touch the diamond or have access to it. Everything is caged or handled in gloveboxes. There is no physical way of touching the diamond.”

The laboratory and independent security personnel monitor sample processing and handling at all times. Macro diamond concentrate handling is verified and documented to ensure an audit trail for sample integrity. The lab follows ISO/IEC 17025:2005 international standard principles. As an internal quality control measure to validate accurate recovery, every sample is picked three times by three different randomly selected people. At each stage, the lab implements quality control measures to ensure the required recovery can be achieved and verified.

On the micro diamond side, additional security measures are also in place. “We randomly spike the samples with synthetic diamond tracers,” explained Gartner. “The actual number of tracers added to the caustic fusion and the chemical treatment process is unknown to the final observers. Only the control technician and the quality controller know the original count of synthetic stones. As a result, we have secure quality assurance built right into our micro diamond recovery operation.”

The SRC’s innovative efforts have also been recognized formally. The diamond facility was recently awarded the Exceptional Engineering and Geoscience Project Award by the Association of Professional Engineers and Geoscientists of Saskatchewan in recognition of the services it provides to diamond exploration companies in Canada and around the world.

Mike McCubbing, lab supervisor at SRC, has over eight years of experience in the diamond exploration industry with a focus on kimberlite processing. He regularly attends industry trade shows and short courses and has given presentations on quality control and quality assurance in diamond recovery.

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