Like a large bag in the grocery store?
The bank has told me to stop trying to cash that stuff in, so I’m guessing $0.
Essentially nil. If there was even a traceable amount, it would pay to extract it and repackage the potting soil.
More than at the local bank.
I doubt there would be any gold in potting soil, but this guy has found gold in sand from a hardware store:
https://www.youtube.com/watch?v=x1fx1ClmS8w