Salting Drill Core Samples
Salting scams are few and far between, and are usually detected quickly because assay result are abnormally high or do not conform to what might be expected from the geological setting of the region. However, the dubious art is always being refined, and sophisticated methods have been used in some recent salting swindles, including that of Bre-X Minerals at its Busang property in Indonesia.
Salting is the deliberate introduction of metal into a sample, intended to produce a false assay result. There is a long and ignoble history of salting scams in mineral exploration, usually in precious metal exploration, which lends itself to sample tampering. The small amount of gold, silver or platinum needed to affect the result of an assay makes the practice relatively easy. Also, because genuine precious metal mineralization is often not visible to the naked eye, barren and mineralized samples may look similar, making it harder to detect salting.
Often coarse, placer gold is added to barren samples, which results in erratic assay results and so-called “reproducibility problems” far beyond what might be expected from a naturally occur ring deposit with coarse gold. The salting is usually detected through testwork which shows that all of the gold found in the samples is coarse-grained, with little or no fine grains. Normally, if coarse gold occurs in a deposit, there is always plenty of fine gold along with it.
Salting scams are not as common in base metal exploration, though they are not unknown. One reason is that base metal mineralization is usually visible in drill cores and hand specimens, and it is easy to recognize salted barren samples. There may be another reason: base metals just aren’t quite as romantic as precious metals, and don’t stir the imagination of naïve investors. However, even in recent years, the share prices of several juniors have soared to great heights based on visual estimates of the base metal content in drill core. “Eyeball assays” are now frowned upon by securities regulators because, in most cases, the subsequent assays show little or no mineral content, but only a need for the geologists to invest in corrective eyewear.
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