In the last 6 months I have learned a bit of what extractive metallurgy is about. One of my projects involves isolating an element from an ore where the desired element is one of many minor constitutents. What is important here is the term “minor constituents”. When the desired element is a minor constituent, then one necessarily faces the prospect of processing large quantities of mass.
Processing large quantities of mass requires that the material and energy inputs used in the process must be very inexpensive. Except for gold, you have to start thinking of heat as a kind of reagent that can be applied to make things happen. The lucky circumstance with gold is its affinity for cyanide in an oxygenated aqueous environment.
It is a very interesting and worthy challenge to start with rock and contrive to remove purified products from it. Half of the fun is working with the engineers and metallurgists. They have a very different perspective of industry than a stiff like me who has always relied on Aldrich for “raw materials”. I have had to recalibrate a bit. You don’t meet people like this at ACS meetings.
I have spent more than a little time digging into extractive metallurgy from the 19th century. A good deal of fairly sophisticated technology was worked out long ago for many metals on the periodic table. Mostly, what has changed between the metallurgy of yesteryear and today is that we now consider fairly low grade ore as economically viable.
The tailings of yesterday will become the ore of tomorrow. It just depends on the value. When you drive around the gold and silver mining districts in the Colorado Mineral Belt, the tailings that you see from the road have most likely been worked over at least once.
Lamentations on Chemistry 
Two things:
1. “The lucky circumstance with gold is its affinity for cyanide in an oxygenated aqueous environment.” Tell that to the EPA and environmentalists who are most displeases with the cyanide-laced superfund sites in that same Colorado Mineral Belt. There’s been a pretty big impact on water quality up there, but also some great trial wetland treatment systems among other things.
2. “The tailings of yesterday will become the ore of tomorrow.” Along similar lines, note that China is importing a great deal of Powder River Basin coal for their power plants. At a cost of about an order of magnituide higher than the rest of us have been paying, plus transportation costs. Staggering indeed.
Let’s hope that people aren’t wagging their fingers with gold rings on or flapping gums that cover gold crowns. People want and want, but the prospect of cyanide extraction never seems to cross their mind when standing at the counter at Jareds buying gold jewelry. At least cyanide is hydrolyzable or oxidizable. It’s not forever like mercury. There are other extraction schemes like chlorination and lixiviation with thiourea, S2Cl2, or thiosulfate. But oxidizable sulfur in the environment isn’t such a happy thing either.
If you can’t grow the resource, then you have to extract it. We have to be grownups and understand that wanting and having always involves something to do with the ground.
Homily? Epistle? I think you missed your true calling. 🙂
I once was lost but now am found.