The yellow gold came from a claim about 6 miles up river from the white gold which came out from under a false bedrock we had pried up with pry bars and was laying in a white clay. Both are gold, but the whitish one that came from under a rock that was a few billion years old is also gold, it has just been exposed to Mercury over time. Sometimes people discard the white and gray metal as junk, you should not do this.
The proper technique to turn the white or gray material into yellow gold is to use a retort to absorb the Mercury, as prospectors we need to be environmentally friendly, or you can bottle it and send it to a refiner and let them handle it. The old timers would just put it into a cast iron skillet and let it cook of over a fire, which may explain the short life span they had. If you get mercury contaminated gold be safe handling it and keep it under water, Mercury evaporates at 76 degrees F., and once airborne if you inhale it it will be in your body for life.