We used to get rock fines and flour from a from quarries that crushing red granite into gravel. The powder was just waste to them. The rains washed down the very finest dust into a depression below the crusher which we scooped up as a heavy mud.
Good source of very slow release potassium and many trace minerals. If you can get it, I would recommend it.
Go to the garden center and buy lime. It comes in 50 pound bags and is just limestone dust. If you have ever had bloom end rot on your tomatoes the soil could be deficient in calcium. Lime or I suppose any rock dust will cure the problem..
Never tried it, but it is an interesting topic and thanks for raising it.
I wonder if some of the benefit that people have seen is not just from trace minerals but also a result of improved soil structure - e.g., roots being able to grow more easily and further as well as air and nutrient-rich water reaching the roots more easily...