Gold dust and flakes are very similar in purity to gold nuggets. However, there is a major difference. Since the gold nugget is a single unit, is was formed in only one place. On the other hand, gold dust and flakes are small particles. Because of this, and because it takes a lot of effort to gather, often, gold dust and flake samples were collected from multiple locations. However, even like this, most gold dust and flake refinery results are also in the range of eighteen karat (18K). In our experience, very few gold flake and dust material is higher than 18K. Since 2009, here at Portland Gold Buyers, LLC, we have bought gold dust and flakes several dozen times, if not over one hundred times. Of all those times, only two (2) times we bought material that refined at at twenty karat (20K), which is 83% pure.
In my experience, raw gold is very seldom lower than 75% pure, or higher than 90%, after all non-metals have been removed. In this material, a part of the mass is non-metallic. At the time of refining, that mass will float out of the metal mass. Because of this, the after melt weight will be a little lower than the pre-melt weight. It is this mass, the post melt mass, that will be assayed.
Refineries take only pretty clean raw gold batches. Beyond a very minimal amount of non-metal, most refineries will not take the material, because very soon it qualifies as ore. Handing ore is closer to the mining process than to the refining process.
Gold flake ………………….$25,000/kg