Thanks Paul,
I was not aware that pyrite oxidized rapidly enough to produce that much heat. In fact I thought pyrite was mainly found in shales. Does pyrite also form in coal beds?

That brought to mind the Vikings and their 'bog iron' production. I went searching and found this link which describes pea sized iron nodules that form in peat bogs. Apparently the process is fairly rapid because the article mentions that the iron could be reharvested after a generation. [www.hurstwic.org]

BTW, anyone interested in Vikings can go back to the main page and follow links to Viking turf houses, weapons, fighting techniques, shipbuilding, etc.. This is one of the best Viking sites on the web!