Opinion On What Would Cause This.

During the war while Hitler and his troops were pilaging different villages and towns, many people hid their gold in mason jars of "Aqua Regia" and it was hidden in plain sight. The acidic properties of aqua regia are such that silver is immune to any effects. The ones who hid their gold had to then after the war, recover it from the solution, there was generally 2 steps in doing so, first ammonium chloride then sodium metabisulfite