As far as I'm concerned its rather a grey area - Azomite isn't a true rock dust for the methods we use rock dusts for. I will be the first to say that it is in my soil mix but it is actually a volcanic colloidal clay - which, while it has its place in the garden for assorted minerals I would always try and source granite or basalt fines first. Take a look here - great deals and shipping is minimal for basalt and other true rock dusts. Catalog - Rock Dust Local J
Sweet link Jerry! Thanks for posting that. I have not been able to find anyone who can ship without making me pay through the tooth for shipping costs.