If you’re looking for gold, look in trees
https://www.economist.com/science-and-technology/2019/05/25/if-youre-looking-for-gold-look-in-trees [www.economist.com]
2019-05-24 17:47
Prospecting for gold by looking for it in leaves has finally proved itself commercially in Australia
The quantities are minuscule. In areas where there is no gold, leaves may have a background level of 0.15 parts per billion (ppb) of gold; on gold-rich sites that can rise to 4ppb.
source: HN