With Amalgamite, you need no acids, just melt the amalgamiter. Put in your plated material, small dredge nuggets, or your black sands, and stir them undr... The gold qwill go into the Amalgamite and it can...
I have found that one of the best ways to strip gold plating is just plain old Nitric Acid... It attacks the base metal, dissolves it and for the most part in my experience, the gold floats, and heavier pieces...