I'm planning on getting a soil test asap, but am just working over this thought in my head today.
In any case, I'd love to have some for indoor planters, containers,
compost, worm bins, potting soils, seed starting mix, etc.
Here, it would be basalt. I'd love to use rocks off my land, because they are free and local. Maybe I've been listening to too much Coast to Coast AM lately, but one thing I've heard about local foods is the local minerals they contain. These local minerals and their magnetic properties interact with the magnetic lay-lines and field of Earth, thusly having an effect on us. Depends on who you want to believe.
I've heard to heat rocks in a hot fire for 1.5-2 hours, then take them from the fire and toss them into water is a good way to micro-fracture the rock, especially igneous rocks.
Be careful, I guess.
http://www.academia.edu/194444/Fire_Cracked_Rocks_-_An_Archaeological_Experiment