I was imagining that your typical nickel-iron meteorite would have a couple of percent of interesting impurities. I couldn't find any really good sources of in

I was imagining that your typical nickel-iron meteorite would have a couple of percent of interesting impurities. I couldn't find any really good sources of information, but it sounds like -- with the exception of Cobalt -- any other recoverable metals would be in the parts per million, so not worth the trouble. On the other hand my plan to cast meteoritic iron into shells and shoot them to Earth might still be practical, if only there was something suitably valuable to put into them...