EXPLORATION ’93 — Geologists discover the fine art of

Gemmologist Donald Goodger is in demand. Ever since diamonds were discovered

in the Northwest Territories, he has been fielding queries from those eager to join in the search for Canada’s first diamond mine.

There is a surprising rift in knowledge between gemmologists and geologists. Gemmologists such as Goodger generally know little about diamond exploration and mining techniques, and the geologists with whom they deal are largely unacquainted with the intricacies of diamond valuation. A former United Church of Canada minister, Goodger became interested in gems in the early 1960s. He received his gemmology diploma in 1972 and for several years taught a 2-year course in Toronto, sponsored by the Gemmological Association of Great Britain. In the 1980s he combined aspects of both the British and American diplomas and designed a uniquely Canadian course. When Goodger completed his studies, there were about 25 fellows of the Canadian Gemmological Association (CGA). Today the directory lists hundreds of names.

As drilling and bulk-sampling heat up on diamond prospects across the country, it is increasingly important that those involved — from investors to field staff — know the ABCs of gem appraisal.

The current dearth of knowledge became only too evident a few months ago, when the Aber-Commonwealth-SouthernEra joint venture announced the recovery of “canary yellow” microdiamonds in a sample taken from its Tenby claims, near Lac de Gras, N.W.T. The announcement thrilled investors and the stocks of the main players soared.

Use of the word “canary” raised suspicions among the few experts in the business. The adjective is used by appraisers to describe a specific type of rare diamond and does not normally accompany preliminary drill results. But most observers remained in the dark until further tests revealed that the microdiamonds were synthetic stones derived from the drill bit. This revelation damaged the joint venture’s credibility and, for many, continues to be the diamond play’s defining event.

For larger stones, use of a simple hand-held instrument called a “Diamond Beam” can prevent such mistakes, Goodger says. Shaped like a gun, the tester emits a beam of heat into the diamond. A real diamond will quickly dissipate the heat, triggering an alarm in the tester. The device costs about $150 and is considered essential for diamond valuation.

Lakefield Research, which processed the fateful samples, is running tests on a Diamond Beam to determine its reliability. Manager of Analytical Services Russ Calow says that if the tests are positive, Lakefield will use the beam when it processes bulk samples taken this winter.

Gemmologists are likely to be in even greater demand if the Dia Met-BHP joint venture, which made the initial diamond discovery near Lac de Gras, confirms the long-held rumor that the bulk sample from the Point Lake kimberlite contains colored stones, or “fancies.”

Color is one of the “four Cs” (the others being cut, clarity and carat weight) used by gemmologists to determine the value of rough diamonds. Every diamond is different and only about 25% of world production is considered large and clear enough to be cut into gems. The rest are classified as industrials, or near-gems.

“Because of the very great variety in which diamonds occur, they are handled as individual commodities from the moment they are discovered,” says author Eric Bruton in Diamonds, long-considered the gemmologist’s bible. “Except for the very small and imperfect material, every stone is given a classification and value before it is marketed.”

More than 3,000 classifications of diamonds (including combinations of 35 shapes, 14 weights and seven colors) have been developed. The criteria include:

— Cut: Based on several factors including facet symmetry, polish and proportion, the cut determines brilliance, color dispersion and sparkle. Regular octahedrons, which are easily cut in half, are the favored shape. — Color: Colorless diamonds are extremely rare and valuable. But red, blue, pink and canary diamonds also fetch premiums over white stones. At a Christie’s auction last May, for example, a 3.66-carat white diamond sold for US$19,563. A slightly smaller fancy pink fetched US$157,416. — Clarity: This depends on the size, locations and number of inclusions. An otherwise “perfect” diamond can be rendered valueless by an inclusion in the centre of the diamond.

— Carat Weight: The term is derived from the seed of the carob tree. Ancient pearl merchants found that, when dried, the seeds had a uniform weight and could be used as units of weights for pearls.

The heavier the diamond, the rarer and more valuable it is. One carat equals one fifth of a gram. The total weight of diamonds recovered from a 160-ton bulk sample of the Point Lake pipe was 101 carats, and a few of the stones fell into the 1-to-3-carat range. This is considered a significant result for such a statistically small sample.