LETTER TO THE EDITOR — An easily detectable discrepancy in Indonesia

I have followed with great interest The Northern Miner’s reports of the problems facing Bre-X Minerals over the assay results of samples from the Busang property in Indonesia.

It is apparent that initial calculations and procedures based on common sense have been mostly ignored in favor of more complex and time-consuming evaluations.

American Canyon Mining specializes in the dry recovery of heavy minerals, primarily gold, by gravity separation. In order to avoid costly and time-consuming in-depth evaluations of many “high-grade” properties presented to us, we initially concentrate on grain size, shape and weight distribution considerations, which often permit easy detection of the worst exaggerations.

This pre-evaluation is accomplished through simple processing — through the use of a concentrating table or panning — of select samples of the highest-grade material. A condition for the applicability of this low-tech evaluation is the occurrence of free and visible gold in the sample, with grain sizes of no less than about 100 microns. The Busang material, with its large particle size of 100 to 400 microns, would seem perfectly suited for this process.

The weight calculation of the gold particles is based on a specific gravity of 17, a diameter of 100, 250 and 400 microns, and two different shapes — ellipsoids (with a thickness 20% of diameter) and spheres. The number of grains of gold in a 750-gram sample can then be calculated from the gold grade of the sample.

Assuming an even distribution of total weight percentages between the sizes and shapes of the different particles, simple, on-site panning of a few pulverized 750-gram samples (the equivalent of the samples leach-tested by Bre-X) should have resulted, statistically, in the recovery of, on average, about 472 visible gold particles per sample. Typically, smaller grain size fractions make up a larger percentage of the total gold weight. Consequently, the total number of grains can be expected to be higher than the calculated average.

Alternatively, if the gold grades established by Freeport McMoRan Copper & Gold following its due diligence assaying prove to be correct, the same on-site panning would have resulted in the recovery of only one particle.

Given this huge and easily detectable discrepancy, it stands to reason that any pan-wielding junior geologist or technician could have alerted his superiors, at the first exposure of the high-grade Busang samples, to a potentially serious problem in the making.

G. Stromberger,President

American Canyon Mining, Dallas, Tex.