> You can use a germanium diode or even Shottky now instead of a “crystal”.
Or a razor blade or a piece of roofing lead and a needle.
Or a razor blade or a piece of roofing lead and a needle.
Good places to look for them are conductors and crystals.
https://en.wikipedia.org/wiki/Crystal_detector
https://rimstar.org/science_electronics_projects/razor_blade...
Good luck! And don't sneeze once you've found a good spot.
Even true for LEDs!
https://en.wikipedia.org/wiki/Silicon_carbide#Natural_occurr...