Originally Posted by Richard

Azomite and "rock dust" products (e.g., green sand) have two important things in common:

1. Nearly all the minerals listed on the package are in a form unavailable to plants; i.e., covalent compounds.
2. The sources are residuals from rock quarries who would otherwise have to pay to dump this largely unusable by-product somewhere else.

Having said this, I should also point out that either of these are useful as a ONE TIME additive to a soil mix. Soil mixes are typically void of covalent rock subgravels and dusts. When present, they become important catalytic sites for ionic exchange. Again, the plants do not uptake the covalent rock material and so it never leaves the soil mix. There is no benefit but possible negatives to adding it more than once.

While talking about plant products that advertise unusable minerals, I would like to mention that the same is true of the plant hormone products Superthrive, Liquid Seaweed Extract, and Kelp solids. It is the hormones in these products that cause the benefit you see, and not the long list of rock minerals.