I might also add that while both chicken grit and perlite do improve drainage in soils, their shared qualities pretty much ends there. Chicken grits are quite heavy (in weight) and add valuable minerals to the soil, while perlite weighs very little and does not contribute usable nutrients (unless you are growing a particular plant in the small subset of those that use silicon). What we call perlite is really expanded perlite, which is perlite heated to the point of expansion due to the water held inside the rock. Unlike vermiculite (another expanded rock), perlite does not absorb water, but will hold water on its surface due the the rough micro texture. The expanded perlite is usually contaminated with fluorine, but not so much as to cause any problems, except in particular circumstances.
