Hi i got a question i tried gold recovery from full and half plated pins and i did it in 3 batches of HNO3 to get rid of copper in one batch there was a little more of pins containing iron(i totaly forgot about it). And i got brown residue (well my quess is that it is iron). What can i do with that? I'll attach photo here. Now i know that if pins got some iron in it i have to disolve them straight in aqua regia. The thing is i got gold foils trapped with this iron oxide i quess i got 2 small filters of that and a little bit left to filter. And i got 2 batches of only foils. Should i dissolve it all in AR or separate foils from iron oxide in some way ?