When we hear the word "byproduct," it often designates something unwanted or even negative coming out of a decision or process that provides some product or outcome we do want. In the world of mining, however, byproducts are often valuable minerals produced in the course of extracting other desired minerals from their ores. For example, zinc mines often also produce profitable quantities of lead and silver. And, it can be the other way round; gold, silver and copper mines can sometimes also contain profitable quantities of zinc. I mention zinc,…