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To modify a line from the fungi people: "All rocks are lickable. Some rocks are lickable only once."

The dangerous ones are probably also well located on the planet, aren't they?

Lots of them are near geothermal or volcanic features- a toxic sedimentary rock is highly improbable, for instance. Not impossible, but improbable.

I will repeat that to the kids I can witness licking stones next to my place ;)