What are the pros and cons of different rock dusts?
Basalt rock dust: Some sources say basalt rock dust is the optimal kind of rockdust, and I've never heard anyone deny that directly. It has less silica than Azomite and diatomaceous earth, for sure. It is higher in other minerals, however. It is said to be high in ferrous minerals. I've seen differing compositions listed for basalt rockdust.
