Traveller11 said:
Hello packrat
I've been asking some questions about the HCL/H2O2 process you mentioned and I have been unable to get the answers I was looking for. You seem to have a straightforward way of talking so I will ask you.
Will the HCL/H2O2 process remove blacksand, pyrites and other free base metal particles from a placer concentrate screened to -100 mesh?
If the placer gold in this concentrate is only 90% gold, with the rest silver, copper, etc., will the HCl/H2O2 process leave pure gold in the concentrate, to be leached by another process?
Bob
most black sands concentrates tend to have a large quantity of sulphides, which tend to interfere with recovery. a good roast in an oxidizing flame (a cheap mild steel skillet is ok) until cons reach red hot or so, some reccomend up to an hour, will convert sulphides to oxides, & sometimes causes pyrites to "pop" exposing values that may be trapped inside. At this point extreme caution is advised, this process should only be performed outside or under an effective fume hood, as roasting arseno-pyrites releases arsenic, a deadly gas.
Your placer gold is never pure gold, regardless of how pure it looks. It is always alloyed with some other metal. The Acid-Peroxide (AP) seems to work best on exposed base metals, at least in my limited experience, such as the copper underneath fingers, and the copper/brass/nickel alloys in pins, the silver/tin/gold of the solder. On fingers & pins, you will be left with the foils, flat or pin-shaped tubes, as the exposed base metals are exposed. However, the alloy of the gold plating, if any, won't be broken down. it can be dissolved, if you add too much oxidizer &/or heat the solution, which would likely be counterproductive.
Though i have not performed such processes, Poor Man's AR, which is NOT HCl-H2O2 (AP), but heated 50:50 HCl/H2O with incremental additions of a nitrate, either sodium or potassium. I use Gordon's Stump Remover, 99% Potassium Nitrate, from a farm supply store. here in US they are named Tractor Supply, Orchlyns, or Runnings.
http://www.pbigordon.com/pdfs/StumpRemover-MSDS.pdf?zoom_highlight=stump+remover#search="stump remover"
It should dissolve your base metals, leaving you with elemental gold as a brown or black powder. once rinsed, the gold should be able to be leached with HCl-Clorine Bleach, allowing sand residues to be filtered off, then dropped with Sodium Metabisulphite (SMB) or Ferrous Sulphate.
Some may reccomend the use of Nitric Acid for such a process, but it is expensive, & produces much nitric Oxide, also a deadly gas.
If I could make a recommendation, search in the "Prospecting, etc...." topics. Go to lazersteve's signature line & use his google-enhanced search engine & use keywords, like "black sands", "placer gold", "concentrates". There isn't a one post answer to your question, I fear, & in the right section you have access to prospectors, miners, from the world over whose real-life experience & suggestions would carry more weight than mine, I believe.
Sometimes, (I paraphrase from hitchhiker's guide to the Universe series), the "answer to the puzzles of the universe is easy, but asking the right question is hard.
Just my dos centavos, amigo. I hope some of the more experienced members of the forum will chime in on this. They may be more likely to if they find the post under "Prospecting".
Good luck & hang in there.
