[pifi]

Hello,
please can you help me discern what is unsoluable sandy color product of nitric acid leaching?

I expect
Ag , Cu + HNO3 -> produce Ag, Cu nitrates (a blue color solution)
then I expected to place Cu rod into solution to replace Ag into metal crystals.

But...
I started by process Ag-contacts leaching in Nitric acid. Some of contacts were full of Ag, some were only coated by Ag.
Chemical reaction was fast, exotherm. and after few hours all metals were dissolved. But color of solution was not blue (as I saw in internet), but it was opaque, maybe green-blue to sandy color. (AFAIK, nitrates are well soluable in water , so what is it?)
Then I wait 1 day and then this sandy color material precipitate down. Then I filter out this material, and on solution I tried standard process to grow silver on copper rod. With paper filter I catch most of sandy color material, but some remains in solution.
After 1 next day with Cu rod in solution - Nothing happens, the rod have thin layer of something white and something black. It is also weird, what is on copper tube.
After some days, sandy material is still raising in bottle.

Then I try centrifuge. I was able to get out 5mL of some grey-black spot material. Maybe it is a friend of silver. But practically the yield from 250g of contacts must be much higher than 5mL of silver. So I need to save big rest of silver :-(

Thanks...