Cake and Frosting

No, this isn't a Cake Wrecks post, though I was impressed with today's line up of Harry Potter-themed Sunday Sweets. It is, instead, a pointer to a very interesting post in a new blog, Wry Heat, (new to me, at least) on the multiple lives of a large mine. The Copper King Mine has had, by my quick count, six "lives" or phases of active extraction, dependent on the technology and infrastructure available during each phase. The author also predicts a seventh phase, using bacteria to get at mineralization currently out of reach:

The Copper King mine will continue into the future, but what then? All mining since 1870 or any that will occur in the next few decades will have exploited only the top 1000 feet of the 7000-foot thick mineral deposit. Most of the remaining material is low-grade chalcopyrite (about 0.3% copper or less), material not economically extractable now. At that time, will the mine finally be mined out? No! New technological processes will be developed to economically extract some or much of the remaining copper.

One such process under development is the dissolution of chalcopyrite using sulfur-eating bacteria which can exist only in the environment of the sulfide mineralization. When this method is fully developed, it could allow leaching of chalcopyrite in situ (in place underground) and give the mine another life. It could also allow leaching of very low grade mine tailings left from previous mining operations.

Part of what I found interesting was the fact that two new technologies have been developed since I was an undergrad: solvent extraction (cyanide extraction for gold has been around since my day, but I was unaware that a parallel technique had been developed for copper sulfides) and high temperature pressure leaching (of which I was totally unaware). Also, non-geology people should note the ecomic basis of "ore;" I've found that most people simply think of the term as a valuable mineral, rather than something that can be extracted at a profit. The reason it's important to think of it in the latter manner is that it means, as the article so nicely illustrates, that depending on a variety of factors, including (but not limited to) concentration, volume, market prices, technology, and government regulation, bodies of rock that were formally worthless can "become ore," and ore bodies can become "worthless-" or more accurately, not extractable without economic loss. So the existence of ore is as dependent on current conditions as it is on geology.

The central point of the post is that regulatory conditions can interfere with the economics of resource extraction; I agree with that central point. Though the author does not as clearly align himself with the "anti-big-gummint" stance as the first commenter seems to assume, I do suspect that he and I differ on the degree to which environmental (and other) long-term, "external," costs need to be factored in, and, yes, addressed through government regulation.

So what does the title of this post have to do with anything? When I was an undergrad, the primary economic mineral (or element) in a deposit- in the above example, copper- was typically referred to as the "cake." Since the natural processes that concentrate one metallic element will ften concentrate others to a lesser degree, other valuable substances can often be recovered from an ore deposit, as long as you're going to dig it up anyway. Those secondary materials, which often wouldn't be economically feasible to go after on their own, but can offer substantial additional profit in conjunction with the cake, we called "frosting." Another interesting theme of this piece is in the peripheral remarks on how changes in technology have at times allowed extraction of the frosting along with the cake, and at other times, not.