Ok. But how?
Take a leaf and dip it in mercury. Then burn the mercury away. If there is anything shiny, you’re good.
My best guess.
My guess is that a Mass Spectrometer would come in handy for this task. (Or perhaps a tricorder.)
I just put a handful of leaves from a bush out in the back yard and dropped them in my gold pan. They all washed out. No gold I guess.