In searching for an economic deposit of any metal, prospectors use geophysical data to narrow down a region of interest then return to complete sampling and assaying. In an entire region, the prospector will only take a few samples and use that data to determine if a region warrants more exploration work.
When it comes to gold prospecting, this method means that it is very easy to miss an economical gold deposit. Working on such small scales is problematic because it is very easy to, by chance, completely overlook an economic deposit of gold. So how does the prospector improve his odds? There are techniques that can be used to enhance the chances of finding gold. Gold grain abundance and grain characteristics have been applied systematically in the past thirty-five years in the search for gold. The most common characteristics used are size, shape and chemical composition.
Gold grain morphology is an example of one of these techniques. Gold grain morphology takes advantage of the fact that gold is very malleable, and the surface shape of gold will change as the metal travels farther away from its source. Under the gold grain morphology classification system , gold grains are “rated” as either pristine, modified or reshaped. Pristine gold grains have maintained their primary shapes and surface textures. The discovery of pristine grains indicates that you are less than 500 meters to the source of the gold sample. Modified gold grains are slightly reshaped, and the discovery of modified gold grains indicates that you are 0 to 1000 meters away from the source. Reshaped gold grains have been worn down as a result of traveling more than 1000 meters from the source.
One such company using this method is Diamonds North (CVE: DDN), which has used gold grain morphology to assess till samples collected from their projects. During gold grain morphology assessment, in a given till sample of 30 kg to 50 kg all of the gold grains are sorted out and assessed according to the above morphology classification. If a sample area turns up a significant amount of gold grains, then further exploration is completed. Gold Investing News recently spoke with Mark Kolebaba, President of Diamonds North, about the company’s experience using gold grain morphology. “When you have high counts of pristine and modified gold grains, you know that you are close to a bedrock source of gold. High amounts of pristine and modified gold grains in a sample almost always lead to a bedrock source of gold.” Mr. Kolebaba added that the use of gold grain morphology increases the chances of identifying a gold source, over a broad area.
As mentioned above, a 0.5 ppm gold mine may be economical. To put this into perspective, a 50 kg till sample that supports a 0.5 ppm concentration would contain only around 5 gold grains. In normal geochemical analysis a 50 gram sample of the 50 kg till sample may go to the lab for geochemical analysis. What are the chances that one of the gold grains actually makes it into this sample?
This is where the significance of gold grain morphology is readily apparent. In gold grain morphology, all of the gold grains would be pulled out of this sample and their morphology assessed and used to narrow down the location of the bedrock source of the gold. For comparison, normal geochemical data allows prospectors to indicate gold in the parts per billion scale; gold grain morphology allows prospectors to narrow down gold in the parts per trillion scale. When you consider the current price of gold and the small amount of gold actually needed to generate an economic deposit, gold grain morphology is an excellent technique for effectively targeting a potential economically feasible gold deposit.
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