>>5962297
Realistically either peizoelectricity or pyroelectricity could be used. There's also porphyritic materials.
It's possible, especially if there's external force or heat applied.
Alternatively some zinc and copper in a drilled hole with salt water is enough.
Though considering how bright those bulbs were and how steady they were another
alternative to consider is that he had a porphyritic material that was radioactive.
There's an insane number of ways to produce electricity. if I had to guess, I'd assume
the video is a scam but yeah, you can get power from some, "rocks" directly.