It should crush in the hand easily, dry it should sound like glass and the soot on your hands should rinse clean with no soap just water. If it does those three things you have biochar.
Discussion
Brilliant thanks.
How are these used? I have bits of charcoal in the wood stove that I just throw out all winter. Is this the same?
It's is used as a soil amendment. It is a bit different than the charcoal left over from a fireplace. I am still trying to learn about it. Here are some resources from #[7].
Will definitely check it out! Thanks!