Outdoor Soil Question

So I was wondering if "Gob" or unrefined coal in the soil will hurt plants? A buddy of mine asked me to find out because the area where he is growing used to be a mine and there's old deposits of coal and coal gob. I told him I thought he could just dig his holes and fill it with good soil and he would be fine, but will the feeder roots stretching out into these deposits be affected?

+ rep for any help

As a guess, i can't see why it would be a problem, unless is is disproportionately rich in one nutrient. At the end of the day it's just ancient plant matter i guess... Maybe worth doing a bit of research to see what's in it, and then seeing if that can cause any issues. Worth a try though anyway... probably not any help but i tried

Oh, and if you dug big holes, 2x2, i doubt the roots would even make it out of the hole anyway! Should be fine

Depends on the concentration as stated. As some will naturally leach in the mix in your holes. As far as the root go they will tend themselves if they encounter a very harsh enviroment.

Alright cool. I think we're gonna give it a go and see what happens.