Cooked Assays. Detecting Fake Metal Assays
In his book Roughing It, Mark Twain tells the story of a popular assayer who never failed to get spectacular results from all mineral specimens brought to him for testing. The town’s respectable citizens became concerned and conspired to send him a fragment from a carpenter’s grindstone for assaying. When the fabulously rich results were published in a newspaper expose, the popular “assayer” was forced to leave town in great haste.
Phony assay results are as old as the hills, and a favorite ploy of the crook is to point to an “assay discrepancy” once confronted with an independent evaluation of the property he is promoting.
In 1987, the Northwest Mining Association warned that US$250 million was lost that year alone to “dirt-pile swindles”, gold scams based on phony assay results. Sometimes called “desert dirts”, these swindles continue unabated today and often prey on wealthy retirees with little or no knowledge of mineral exploration.
As in Mark Twain’s time, certain laboratories produce data showing exceptionally high concentrations of gold, and some times platinum group metals, in almost every rock sent to them for assaying. Mining professionals never use these laboratories because of their dismal reputations.
Fraud artists have found a number of ways to falsify the results of an assay. Samples themselves may be salted, or an accomplice placed in the assay laboratory to add metal to the chemicals used in the analytical process. Numbers may be falsified or assay certificates counterfeited.
Closely related to the salting scam is the assertion that a deposit contains “unassayable” or “refractory” precious metals that can only be detected using a ”proprietary” technique. This is the realm of quack science, in which con men and deluded pretenders talk the language of chemistry and metallurgy with out regard for the scientific method.
The con artists use any number excuses to explain why conventional chemical techniques cannot find their gold. Some say that their gold is “micro-fine” or in “micro-clusters” that take on chemical characteristics that prevent them from being assayed. This explanation flies in the face of overwhelming evidence that when the particles of a substance are more finely divided, it will react more readily with other substances and be extracted more easily from its matrix.
Other unassayable-gold promoters declaim about “encapsulation” by other minerals, usually silica, arguing that the surrounding minerals seal off the old from assay fluxes and leaching acids. Yet there are dozens of a strong acid attacks and reactive fluxes that will destroy any “encapsulating” minerals. A third scapegoat is “interference” by other elements, which is alleged to prevent analytical instruments from detecting the metals of interest. The problem is well-known in analytical chemistry and a capable chemist can find ways to eliminate the interfering elements.
In short, there is always a legitimate and reasonable chemical argument that can be made against a claim of “unassayable” gold. There are also a number of analytical methods, such as neutron-activation analysis, that are not sensitive to the supposed causes of unassayable metal. Nevertheless, the investor will usually be a layman unacquainted with analytical chemistry and must, instead, keep his eyes open for red flags and other signals that a project is far from legitimate.
In the early 1980s, the Canadian Institute of Mining and Metallurgy published a paper debunking the myth of “unassayable” deposits. The authors investigated many of these projects and found that in every case, the fabulous numbers reported from unconventional assaying methods were the result of technical incompetence or outright fraud
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