I just saw this presentation at the Chaos Computer Club conference, for an “Ethical Hardware Kit with a PCB microcontroller made of wild clay retrieved from the forest in Austria and fired on a bonfire. Our conductive tracks use urban-mined silver and all components are re-used from old electronic devices”. It was part of the feminist hardware strand!
Thats pretty cool. Would be interesting how much of a usable Computer could be build with this approach.