The Virtues of High Grade Deposits"High-grade deposits, some large, others relatively small, can be financially very attractive. A recent example of low versus high grade is provided by Barrick Corporation’s Post-Betze open pit and the nearby Meikle underground operation in Nevada (Figure 1). The Post-Betze deposit has over ten times as much gold as the Meikle deposit. However, extraction of the Post-Betze resource has required construction of a huge open pit and very large waste dumps. From 1996 to 2001, the much smaller Meikle mine produced between 30 to 80% of the ounces produced at Post-Betze, but with a much-reduced tonnage due to its high grade. Meikle was also an extremely low
cost producer.
"There are significant exploration implications of searching
for either high-grade deposits or in situ mining targets. High-
grade deposits are difficult to find — small needles in a very
large haystack. Few companies have made grade the primary
focus of their exploration efforts. To do so requires an excellent
understanding of structural geology, since most of these depos-
its are structurally controlled. It also requires state-of-the-art
exploration tools, particularly geophysics. To properly evaluate
an in situ mining target requires robust rock mass, fracturing,
geochemical, and hydrogeological information, as well as typical
grade and tonnage data. Currently, most economic geologists
are not trained to gather and evaluate such information, cer-
tainly not in an integrated fashion."
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