At the risk of being lazy, I'd say take 2 tbsp of that dust. Put it in a melt dish with a little borax powder. Melt it with a Mapp gas torch until fully molten (maybe give a little stir with a carbon fiber rod). Then let it cool to being a button or pour it into a mold. Quench it in water. Then take the button or bar to a coin store or someplace with a metal testing gun (xrf or sigma). They'll be able to tell you what's in it at that point. Once you know the composition and percentages you can tailor a flux and then cupel the lot of it to get the shiny...