This thread is a bit pathetic. All you need is dust from a gravel operation that is crushing granite (because it happens to be local) into gravel.
Currently granite countertops are a big business and cutting/grinding/polishing creates a source for granite dust.
The idea behind rock dust is sound in that fresh finely ground rock would contain slow-release minerals. Mostly these would be igneous type rocks but sedimentary is especially good for calcium. Many soil amendments are just that- ground rocks.
If your soil contains rock you can release it's mineral content by ph adjsutment and in healthy soil plant roots can find them andd use exudates or microbial association to release them. If your soil is old and weathered, abused by cropping, or washed out sand the minerals may just be absent.
For about $20 you can get a couple of gallons of micronutrients (enough for acres) and drench or foliar spray them or like CM said use a granule.
In sand, I think lots of that runs out. To make my own slow release micronutrient package I soaked three drums of homemade charcoal with the liquid micronutrients then added that material to a high quality home made compost for a few weeks. I've put a wheelbarrow load of that around each tree and expect that should hold enough micronutrients for quite a while.
Making the charcoal:
Soaking the crushed charcoal:
Spreading the product: