LETTERS TO THE EDITOR — Certification would solve assay

I’m sure your report on the Alberta Stock Exchange’s concerns about the validity of gold assays coming from some U.S. laboratories had many of our Canadian commercial assayers both bemused and somewhat surprised (see “ASE requests fire assays of Focal drill samples,” T.N.M., May 24/93).

The pitfalls in performing gold assays by acid digestion followed by atomic absorption are well-documented; indeed, during the 1970s and early 1980s, atomic absorption for gold was virtually ridiculed by many geologists, even when it was only being used to finish the fire assay. I can well remember a major client in the mid-1980s (ah, those good old days) telling me to repeat several hundred AA-finished fire assays because the only reliable fire assay was a classical one in which the gold bead is weighed. No one ever seemed to question how pure the gold bead was. All that aside, the record shows that fire assay is still the best procedure for gold-assaying for two reasons. First, it is a very “forgiving” technique, producing a reliable result even when conditions are not ideal; second, it analyses a much larger sample than most other analytical techniques (typically 10 to 30 grams), which is a definite plus when dealing with nasty things like nuggety gold samples. However, a large part of most gold-assaying problems is not the particular analytical method but the size of the sample. Thirty grams may sound like a big sample, but it is often an order of magnitude or two too small to be truly representative.

The whole hullabaloo over faulty gold assays could have been avoided had there been a national or international laboratory certification scheme for mineral assay laboratories backed by a legal or regulatory requirement to belong. Otherwise, in the present economy, few laboratories can afford to sign up unless it can be proven to benefit the bottom line. And I can guarantee that even fewer clients will be willing to cover the extra costs. Gwendy Hall’s comments (“Assay accuracy not linked to cost,” T.N.M., May 24/93) are well-taken, but I’m sure most commercial assayers would just drool to get a client to pay $50 for a gold assay. Hey, we’ll do it for $25 and throw in a free sample bag.

George Duncan

President

Accurassay Laboratories

Kirkland Lake, Ont.