I have a beautiful one... with lots of enclosures.
I watch it nearly every day and can see how the "mountains are moving" in a time loop. The so nicely polished surface is getting small holes with rust, smashed from within as if I was throwing the piece on the flour, colored points appearing where it was transparent.
It's really my favorite one, showing how stones are bursting with life.
How do you define life? Which force is driving it within to change and not earlier?