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That's just powered by a battery with dissimilar metals, isn't it? Kids do this kind of thing in science class all the time making potato batteries.
Did anyone else use the LM3909 chip to build an LED flasher, back in the day? It would blink once a second for 2+ years on a single D-cell battery.

https://hackaday.com/2018/01/04/there-once-was-an-ic-dedicat...

OK, how does this work exactly?
It's a battery-cell using ferrite (the rock) and aluminium foil as electrodes and his hand as electrolyte. This produces ~0.7v which he then steps up using something like a joule thief circuit[1].

[1]: https://en.wikipedia.org/wiki/Joule_thief