How to Interpret Assay Values
January 2018 by Don Robinson
This assay system of ounces per ton sounds simple enough, but the use of the metric system and the additional measuring terms of “grams per ton” and “parts per million” (ppm) has created some misunderstanding of ore value.
Looking at the exceptions to the basic rules is sort of an advanced prospecting discussion, but the readers of ICMJs Prospecting and Mining Journal are plenty able to handle it.
In processing gold, silver and other valuable ores, the minerals containing the values, such as metallic gold, silver-bearing sulfides or other minerals, must be freed from the surrounding host rock before those valuable minerals can be captured.
Let’s set up a thought experiment: Suppose you had some material that ran one ounce per ton gold, which is generally considered high grade to fantastic grade depending on the circumstances.
Which comes first, claim filing or staking?
Some ask if a prospector can collect an entire ounce in a day. It is possible; I’ve done it before.
My intention was to end this discussion with waypoints and routes, then I found USGS maps of the Plainfield Quadrangle.
While recovery rates are important, they must necessarily be secondary to the volume of material processed. Running more material at lower recovery rates is generally preferable to increasing the efficiency of the system.
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