Ever wonder what happens to the gold scrap you sell? I went directly to a gold buyer in the Diamond District who sells to large refineries. And it was an interesting experience.
I went into a building and up several floors to a small office manned by a burley looking guy who was stoking the fires of several furnaces. He wouldn't let me photograph him, but this is the room where he works:
He took the miscellaneous pieces of metal I brought with me (yellow gold, silver, white metal, whatever) and he put it in what looked like a loaf pan in one of the smaller furnaces. He layered salt peter, sodium nitrate, and boric acid on top of it. (The room is well ventilated.) The objective is to burn away all the miscellaneous “crud” (for lack of a better word) and to melt the metals. Below please find the gold as it is cooking in the loaf pan. This loaf pan is pure graphite, which is the only material that holds up to the heat of the liquid metal.
As it cools, it solidifies and the gold separates from the other metals. The gold portion is removed and drilled in two spots (which allows them to use a spectrum analyzer which says how much gold, silver, platinum, lead and other metals are in the chunk). We started with 407 pennyweights of metal and ended up with only 135 pennyweights of 24K shown in the below photo. 
I should have asked the next step. I believe this gold is sold to a larger refiner who processes until all the porosity and impurities are removed and it can be sold back to us to use for our purposes.