Answer:
My head bobs lazily in the sun. You think I'm cute. For my face is yellow my hair is white and my body is green.
The ones who see it may go blind, Contracting the fool's madness. You have to dig to find it, Crush big stones or mine it. Wash dirt clumps in a pan and wait for it to settle, A shiny, precious metal.
Take one out and scratch my head, I am now black but once was red.
You use a knife to slice my head. And weep beside me when I am dead.
Three lives have I. Gentle enough to soothe the skin. Light enough to caress the sky. Hard enough to crack rocks.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?