Kelowna lab a strategic advantage for Dia Met

The current diamond exploration rush owes much to a private laboratory nestled in a modest industrial building on the outskirts of this Okanagan community. For it was here that much of the analytical work was done that led to the first discovery of diamondiferous kimberlites in the Lac de Gras region of the Northwest Territories.

The lab is owned by C.F. Minerals which was founded in 1977 by geologist Charles Fipke who went on to form Dia Met Minerals (TSE) and make the initial diamond discoveries at Lac de Gras. Today, it is primarily used by Dia Met and partner BHP Minerals Canada to find diamondiferous kimberlites and help determine which is most likely to go into production at the earliest possible date.

The lab is an important strategic advantage for the joint venture, which relies heavily on sophisticated geochemical methods to differentiate between diamondiferous and barren kimberlites without drilling. This approach is considerably more rigorous than that used by juniors who rely solely on geophysics to outline “bull’s-eye anomalies” and “circular pipe-like features.”

The exploration strategy involves locating diamond indicator minerals in surface samples and tracing these up-ice and up-stream to their sources. These indicators are then quantified and qualified to pinpoint target pipes and to allow the joint venture to predict the grade of kimberlite pipes at an early stage of exploration.

The process begins in the field, where a line of sampling can take place as widespread as every half-kilometre or down to 200 metres. A 6-mesh screen is used in the field to remove the coarse material and pre-concentrate the till and esker samples to 10 kg.

During a recent lab tour, The Northern Miner was shown the circuit used to process a standard 10-kg sample. The process begins with wet sieving and heavy liquid separation, followed by magnetic and electromagnetic separation, hand-picking of grains under binocular microscopes, and computer analysis of each grain scanned under an electron microscope. Core samples of 70 kg are also processed after crushing in a small ball mill.

Charles Fipke said the entire front end of the process — the wet sieving and heavy mineral separation — was custom-designed and is patented in Canada, the U.S. and many other countries.

Samples, four bags at a time, are loaded into a bank of screens and mechanically sieved to allow for discarding of light quartz fractions and removal of clay. The process includes a jig cycle which separates the coarser fractions from the fine fractions.

Samples are then oven-dried and poured into hourglass-shaped beakers to go through the heavy-liquid separation cycle. The samples are first poured into a tetra-bromo-ethane solution which has a specific gravity of about three and allows for the removal of light minerals which float. A closed circuit is used and the solution is re-used after being filtered three times to avoid contamination of samples.

The samples are then washed in acetone, which is also filtered for ongoing use in the circuit. After drying, the concentrated sample

is poured into another, more expensive heavy media liquid (specific gravity: 3.3) to remove more lights and further reduce the size of the sample. Fipke said this second stage is often omitted in South Africa where, because of low labor costs, more grains are hand-picked.

Since they have a specific gravity greater than 3.3, the indicator minerals are captured in the remaining samples, which are again oven-dried. The magnetic and electromagnetic separation process begins with the removal of magnetites. The remaining material goes into a stronger magnetic field for further separation into magnetics and non-magnetics. The pyrope garnets and chrome diopsides are thus separated from regional garnets, and a conductivity separation process removes the metallic chromites and picroilmenites from regional garnets and gangue material.

Technicians then examine the samples under microscopes and pick out grains of interest which are then mounted into an epoxy cell and polished. Two electron microscopes (two more have been ordered) are used to scan and color-digitize the grains. One or two experienced professionals will then examine the print-outs and circle grains which could have formed with diamonds. A second scan determines the chemical composition of the selected grains using a computer program designed especially for the purpose. The database used is comprehensive, allowing, for example, for classification of four types of G10 garnets. The second scan does not require a computer operator. The information generated by this process is then merged with another computer, which plots and prints the results on to site maps. This computer program also originated in-house and allows the joint venture to pinpoint areas of interest in the field.

The joint venture also obtains important information from micro-diamonds which are recovered in a fusion process which destroys everything except diamond and corundum. The fusion residues are centrifuged and then analysed by the high-intensity, scanning, electron microscope which can detect diamonds down to two microns.

The lab operates 24 hours per day, five days a week, and provides full-time employment to about 22 Kelowna residents.