At our Maui pawn shop, we melt down old jewelry in a small crucible. No matter what goes in, the product that comes out is almost always just under 60% gold (because of the average mix of 10-, 12-, 14-, 18- and 22-karat gold that people bring us).
That’s just a preliminary step. The video by The Precious Metals West Blog shows what happens next. We at Kamaaina Loan don’t do this; it’s an industrial process that uses a very nasty substance, aqua regia (a mixture of hot, fuming nitric and hydrochloric acids), that only pros with special equipment mess with.
Aqua regia dissolves gold; it is the only thing that will. This is how we recover diamonds. The gold is dissolved, but the diamonds are not affected.
This is safer than trying to pry diamonds from settings, which can break or chip them.