I'm struck by the correspondence between pre-Renaissance recipes for creating the Philosopher's Stone and the modern process of extracting gold from ore. The first stamp mills were built more than a thousand years ago; it occurred to me that the instructions for the transmutation of gold might have been a practical recipe actually employed in ancient stamp mills. Lacking a modern chemical science and nomenclature as we now know it, and desiring to protect their trade secrets, they might have couched their steps in bizarre metaphor, only understandable to a guildsman or acolyte - it wouldn't do for everyone to be able to produce gold! For further protection they might have scrambled the order of the steps.
The seven steps in the process, according to Hermes Trimestigus' Emerald Tablet and conventionally interpreted are:
- Calcination - a thermal or chemical treatment to cause decomposition of ore
- Dissolution - dissolving a substance to yield a solution
- Separation - transform a mixture or solution into distinct products
- Conjunction - recombination of the products into a new substance
- Fermentation - creation of an amalgam for the strengthening of the product
- Distillation - the boiling and condensation of the product to increase its purity
- Coagulation - the final precipitation or sublimation of the product.
At the stamp mill, the Merrill-Crowe gold and silver recovery process is employed.
- Calcination, The ore is crushed
- Conjunction - The crushed ore is passed over mercury swept onto wide copper plates; the mercury combines with gold and silver in the ore forming an amalgam.
- Dissolution - The amalgam is dissolved in cyanide to create the pregnant solution.
- Fermentation - Chemical processes are applied to purify the solution.
- Distillation - Mechanical and thermal processes are applied to purify the solution.
- Separation - Zinc is introduced to the solution; since mercury has a higher affinity for the zinc, all the gold and silver recovered through the process is...
- Coagulation - precipitated out in a pure state.
In an alternative process at some stamp mills including at Bodie, the gold is recovered by evaporating the mercury. At Bodie, the Merrill-Crowe process was a secondary process applied to ore remaining after the simpler initial process.
A speculative point I would make is that from the point of view of the ancient alchemists it might have appeared to them that their process actually transmuted base ore into gold and silver; it certainly looks that way today when you are at the mine looking at the raw ore.
There's much debate about the order and meaning of the alchemical steps in the transmutation of gold; but Merrill-Crowe has it definitively worked out, it's a trade secret no longer! I recognize that there is also a large body of philosophical work associated with the philosopher's stone, it is probable that the ancients attempted to encode many layers of information into their recipes - the method for the production of gold was only one of many intellectual endeavors that had to be hidden in the Middle Ages; here I am showing that the alchemical process was actually a practical and important precursor to modern science.
P.S. Of course, these assignations to the alchemical steps are mine, someone with better chemical or mining knowledge than myself might do it differently, and maybe the Emerald Tablet steps are actually correct.
P.P.S., in case you're curious where this tangent comes from, one of my hobbies is the study of the history of science.