Geologically, lead is often found in the presence of silver, and silver in the presence of Gold. The alchemist’s of old attempted to turn lead into Gold based on the theory that metals in the ground went through a natural transformation with the passage of time – lead became silver, which in turn became Gold.
The alchemists were wrong, but they were not mystical nutcases; they were attempting to speed up what they believed to be a natural geological process.