Perhaps the most notable thing about skim placers is that they form on the top surface of gravel bars, as opposed to coarser gold placers where the weight of the gold particles allows the gold to settle down on or near bedrock.

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.

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.