I used a handful of Azomite in a gritty-style mix last year. To be honest, I didn't notice any effect--positive or negative. I was growing warm-season veggies and used the larger size Azomite, so it may not have had sufficient time to break down. It takes microbial action to break down minerals and I may not have had a sufficiently active microherd. If I was to do it again, I'd try the micronized (finer grind) Azomite. At the rate I applied--let's say 1/2 cup per 5-7 gal container, it wouldn't have a bearing on pH.