Best soil I ever made using bags was with bone, blood, iron, and 10 years of used organic veggie potting soil. I also had great results making a tea with espoma organic veggie fert.
Super soil made with a base of ProMix BX was amazing too.
The compost pile with bananas, eggshells, dandelions, grass, leaves, fruits, veggies, weeds, weed...was to date the most amazing grow ever. I did hit it with one dose of PK (Mad Farmer MOAB) at the start of flower because it didn't look like it was flowering nearly as well as it's sister in the Super Soil. Results were amazing. No burnt tips on the long skinny Mulanje sativa leaves. No bugs!
Now my TGA Jesus OG is re-vegging in that spot and is already throwing out dark green new growth!
@Pattahabi - maybe the mixture of ash and lava dust made cement? The remainder of the soil was super soil and more worm castings. When I removed the plant a week later (it was not happy) and put it in a smart pot full of Super Soil it responded immediately and gave me some nice buds
I used a sledge hammer and just dropped it repeatedly on the lava rocks to break them up. Some were hard as metal and others were soft. I want to get some volcanic sand to try in my soil in the future. I want that nice volcano flavor from Hawaii!
Cheers,
Mo